RFC2828 - Internet Security Glossary

Network Working Group R. Shirey

Request for Comments: 2828 GTE / BBN Technologies

FYI: 36 May 2000

Category: Informational

Internet Security Glossary

Status of this Memo

This memo provides information for the Internet community. It does

not specify an Internet standard of any kind. Distribution of this

memo is unlimited.

Abstract

This Glossary (191 pages of definitions and 13 pages of references)

provides abbreviations, eXPlanations, and recommendations for use of

information system security terminology. The intent is to improve the

comprehensibility of writing that deals with Internet security,

particularly Internet Standards documents (ISDs). To avoid confusion,

ISDs should use the same term or definition whenever the same concept

is mentioned. To improve international understanding, ISDs should use

terms in their plainest, dictionary sense. ISDs should use terms

established in standards documents and other well-founded

publications and should avoid substituting private or newly made-up

terms. ISDs should avoid terms that are proprietary or otherwise

favor a particular vendor, or that create a bias toward a particular

security technology or mechanism versus other, competing techniques

that already exist or might be developed in the future.

Table of Contents

1. IntrodUCtion . . . . . . . . . . . . . . . . . . . . . . . . . 2

2. Explanation of Paragraph Markings . . . . . . . . . . . . . . 4

2.1 Recommended Terms with an Internet Basis ("I") . . . . . . 4

2.2 Recommended Terms with a Non-Internet Basis ("N") . . . . 5

2.3 Other Definitions ("O") . . . . . . . . . . . . . . . . . 5

2.4 Deprecated Terms, Definitions, and Uses ("D") . . . . . . 6

2.5 Commentary and Additional Guidance ("C") . . . . . . . . . 6

3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 6

4. References . . . . . . . . . . . . . . . . . . . . . . . . . . 197

5. Security Considerations . . . . . . . . . . . . . . . . . . . 211

6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 211

7. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 211

8. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 212

1. Introduction

This Glossary provides an internally consistent, complementary set of

abbreviations, definitions, explanations, and recommendations for use

of terminology related to information system security. The intent of

this Glossary is to improve the comprehensibility of Internet

Standards documents (ISDs)--i.e., RFCs, Internet-Drafts, and other

material produced as part of the Internet Standards Process [R2026]--

and of all other Internet material, too. Some non-security terms are

included to make the Glossary self-contained, but more complete lists

of networking terms are available elsewhere [R1208, R1983].

Some glossaries (e.g., [Raym]) list terms that are not listed here

but could be applied to Internet security. However, those terms have

not been included in this Glossary because they are not appropriate

for ISDs.

This Glossary marks terms and definitions as being either endorsed or

deprecated for use in ISDs, but this Glossary is not an Internet

standard. The key Words "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",

and "OPTIONAL" are intended to be interpreted the same way as in an

Internet Standard [R2119], but this guidance represents only the

recommendations of this author. However, this Glossary includes

reasons for the recommendations--particularly for the SHOULD NOTs--so

that readers can judge for themselves whether to follow the

recommendations.

This Glossary supports the goals of the Internet Standards Process:

o Clear, Concise, and Easily Understood Documentation

This Glossary seeks to improve comprehensibility of security-

related content of ISDs. That requires wording to be clear and

understandable, and requires the set of security-related terms and

definitions to be consistent and self-supporting. Also, the

terminology needs to be uniform across all ISDs; i.e., the same

term or definition needs to be used whenever and wherever the same

concept is mentioned. Harmonization of existing ISDs need not be

done immediately, but it is desirable to correct and standardize

the terminology when new versions are issued in the normal course

of standards development and evolution.

o Technical Excellence

Just as Internet Standard (STD) protocols should operate

effectively, ISDs should use terminology accurately, precisely,

and unambiguously to enable Internet Standards to be implemented

correctly.

o Prior Implementation and Testing

Just as STD protocols require demonstrated experience and

stability before adoption, ISDs need to use well-established

language. Using terms in their plainest, dictionary sense (when

appropriate) helps to ensure international understanding. ISDs

need to avoid using private, made-up terms in place of generally-

accepted terms from standards and other publications. ISDs need to

avoid substituting new definitions that conflict with established

ones. ISDs need to avoid using "cute" synonyms (e.g., see: Green

Book); no matter how popular a nickname may be in one community,

it is likely to cause confusion in another.

o Openness, Fairness, and Timeliness

ISDs need to avoid terms that are proprietary or otherwise favor a

particular vendor, or that create a bias toward a particular

security technology or mechanism over other, competing techniques

that already exist or might be developed in the future. The set of

terminology used across the set of ISDs needs to be flexible and

adaptable as the state of Internet security art evolves.

2. Explanation of Paragraph Markings

Section 3 marks terms and definitions as follows:

o Capitalization: Only terms that are proper nouns are capitalized.

o Paragraph Marking: Definitions and explanations are stated in

paragraphs that are marked as follows:

- "I" identifies a RECOMMENDED Internet definition.

- "N" identifies a RECOMMENDED non-Internet definition.

- "O" identifies a definition that is not recommended as the first

choice for Internet documents but is something that authors of

Internet documents need to know.

- "D" identifies a term or definition that SHOULD NOT be used in

Internet documents.

- "C" identifies commentary or additional usage guidance.

The rest of Section 2 further explains these five markings.

2.1 Recommended Terms with an Internet Basis ("I")

The paragraph marking "I" (as opposed to "O") indicates a definition

that SHOULD be the first choice for use in ISDs. Most terms and

definitions of this type MAY be used in ISDs; however, some "I"

definitions are accompanied by a "D" paragraph that recommends

against using the term. Also, some "I" definitions are preceded by an

indication of a contextual usage limitation (e.g., see:

certification), and ISDs should not the term and definition outside

that context

An "I" (as opposed to an "N") also indicates that the definition has

an Internet basis. That is, either the Internet Standards Process is

authoritative for the term, or the term is sufficiently generic that

this Glossary can freely state a definition without contradicting a

non-Internet authority (e.g., see: attack).

Many terms with "I" definitions are proper nouns (e.g., see:

Internet Protocol). For such terms, the "I" definition is intended

only to provide basic information; the authoritative definition is

found elsewhere.

For a proper noun identified as an "Internet protocol", please refer

to the current edition of "Internet Official Protocol Standards" (STD

1) for the standardization state and status of the protocol.

2.2 Recommended Terms with a Non-Internet Basis ("N")

The paragraph marking "N" (as opposed to "O") indicates a definition

that SHOULD be the first choice for the term, if the term is used at

all in Internet documents. Terms and definitions of this type MAY be

used in Internet documents (e.g., see: X.509 public-key certificate).

However, an "N" (as opposed to an "I") also indicates a definition

that has a non-Internet basis or origin. Many such definitions are

preceded by an indication of a contextual usage limitation, and this

Glossary's endorsement does not apply outside that context. Also,

some contexts are rarely if ever expected to occur in a Internet

document (e.g., see: baggage). In those cases, the listing exists to

make Internet authors aware of the non-Internet usage so that they

can avoid conflicts with non-Internet documents.

Many terms with "N" definitions are proper nouns (e.g., see:

Computer Security Objects Register). For such terms, the "N"

definition is intended only to provide basic information; the

authoritative definition is found elsewhere.

2.3 Other Definitions ("O")

The paragraph marking "O" indicates a definition that has a non-

Internet basis, but indicates that the definition SHOULD NOT be used

in ISDs *except* in cases where the term is specifically identified

as non-Internet.

For example, an ISD might mention "BCA" (see: brand certification

authority) or "baggage" as an example to illustrate some concept; in

that case, the document should specifically say "SET(trademark) BCA"

or "SET(trademark) baggage" and include the definition of the term.

For some terms that have a definition published by a non-Internet

authority--government (see: object reuse), industry (see: Secure Data

Exchange), national (see: Data Encryption Standard), or international

(see: data confidentiality)--this Glossary marks the definition "N",

recommending its use in Internet documents. In other cases, the non-

Internet definition of a term is inadequate or inappropriate for

ISDs. For example, it may be narrow or outdated, or it may need

clarification by substituting more careful or more explanatory

wording using other terms that are defined in this Glossary. In those

cases, this Glossary marks the tern "O" and provides an "I"

definition (or sometimes a different "N" definition), which precedes

and supersedes the definition marked "O".

In most of the cases where this Glossary provides a definition to

supersede one from a non-Internet standard, the substitute is

intended to subsume the meaning of the superseded "O" definition and

not conflict with it. For the term "security service", for example,

the "O" definition deals narrowly with only communication services

provided by layers in the OSI model and is inadequate for the full

range of ISD usage; the "I" definition can be used in more situations

and for more kinds of service. However, the "O" definition is also

provided here so that ISD authors will be aware of the context in

which the term is used more narrowly.

When making substitutions, this Glossary attempts to use

understandable English that does not contradict any non-Internet

authority. Still, terminology differs between the standards of the

American Bar Association, OSI, SET, the U.S. Department of Defense,

and other authorities, and this Glossary probably is not exactly

aligned with all of them.

2.4 Deprecated Terms, Definitions, and Uses ("D")

If this Glossary recommends that a term or definition SHOULD NOT be

used in ISDs, then either the definition has the paragraph marking

"D", or the restriction is stated in a "D" paragraph that immediately

follows the term or definition.

2.5 Commentary and Additional Guidance ("C")

The paragraph marking "C" identifies text that is advisory or

tutorial. This text MAY be reused in other Internet documents. This

text is not intended to be authoritative, but is provided to clarify

the definitions and to enhance this Glossary so that Internet

security novices can use it as a tutorial.

3. Definitions

Note: Each acronym or other abbreviation (except items of common

English usage, such as "e.g.", "etc.", "i.e.", "vol.", "pp.", "U.S.")

that is used in this Glossary, either in a definition or as a subpart

of a defined term, is also defined in this Glossary.

$ 3DES

See: triple DES.

$ *-property

(N) (Pronounced "star property".) See: "confinement property"

under Bell-LaPadula Model.

$ ABA Guidelines

(N) "American Bar Association (ABA) Digital Signature Guidelines"

[ABA], a framework of legal principles for using digital

signatures and digital certificates in electronic commerce.

$ Abstract Syntax Notation One (ASN.1)

(N) A standard for describing data objects. [X680]

OSI defines functionality in layers. Information objects at higher

layers are abstractly defined to be implemented with objects at

lower layers. A higher layer may define transfers of abstract

objects between computers, and a lower layer may define transfers

concretely as strings of bits. Syntax is needed to define abstract

objects, and encoding rules are needed to transform between

abstract objects and bit strings. (See: Basic Encoding Rules.)

separate words in a name are indicated by capitalizing the first

letter of each word except the first word. For example, the name

of a CRL is "certificateRevocationList".

$ ACC

See: Access control center.

$ access

(I) The ability and means to communicate with or otherwise

interact with a system in order to use system resources to either

handle information or gain knowledge of the information the system

contains.

(O) "A specific type of interaction between a subject and an

object that results in the flow of information from one to the

other." [NCS04]

communicate with a system, including one-way communication in

either direction. In actual practice, however, entities outside a

security perimeter that can receive output from the system but

cannot provide input or otherwise directly interact with the

system, might be treated as not having "access" and, therefore, be

exempt from security policy requirements, such as the need for a

security clearance.

$ access control

(I) Protection of system resources against unauthorized access; a

process by which use of system resources is regulated according to

a security policy and is permitted by only authorized entities

(users, programs, processes, or other systems) according to that

policy. (See: access, access control service.)

(O) "The prevention of unauthorized use of a resource, including

the prevention of use of a resource in an unauthorized manner."

[I7498 Part 2]

$ access control center (ACC)

(I) A computer containing a database with entries that define a

security policy for an access control service.

implement access control in a key distribution system for

symmetric cryptography.

$ access control list (ACL)

(I) A mechanism that implements access control for a system

resource by enumerating the identities of the system entities that

are permitted to access the resource. (See: capability.)

$ access control service

(I) A security service that protects against a system entity using

a system resource in a way not authorized by the system's security

policy; in short, protection of system resources against

unauthorized access. (See: access control, discretionary access

control, identity-based security policy, mandatory access control,

rule-based security policy.)

an unauthorized manner by an entity that is authorized to use the

resource in some other manner. The two basic mechanisms for

implementing this service are ACLs and tickets.

$ access mode

(I) A distinct type of data processing operation--e.g., read,

write, append, or execute--that a subject can potentially perform

on an object in a computer system.

$ accountability

(I) The property of a system (including all of its system

resources) that ensures that the actions of a system entity may be

traced uniquely to that entity, which can be held responsible for

its actions. (See: audit service.)

of security breaches.

$ accredit

$ accreditation

(I) An administrative declaration by a designated authority that

an information system is approved to operate in a particular

security configuration with a prescribed set of safeguards.

[FP102] (See: certification.)

of the system's security mechanisms. The terms "certification" and

"accreditation" are used more in the U.S. Department of Defense

and other government agencies than in commercial organizations.

However, the concepts apply any place where managers are required

to deal with and accept responsibility for security risks. The

American Bar Association is developing accreditation criteria for

CAs.

$ ACL

See: access control list.

$ acquirer

(N) SET usage: "The financial institution that establishes an

account with a merchant and processes payment card authorizations

and payments." [SET1]

(O) "The institution (or its agent) that acquires from the card

acceptor the financial data relating to the transaction and

initiates that data into an interchange system." [SET2]

$ active attack

See: (secondary definition under) attack.

$ active wiretapping

See: (secondary definition under) wiretapping.

$ add-on security

(I) "The retrofitting of protection mechanisms, implemented by

hardware or software, after the [automatic data processing] system

has become operational." [FP039]

$ administrative security

(I) Management procedures and constraints to prevent unauthorized

access to a system. (See: security architecture.)

(O) "The management constraints, operational procedures,

accountability procedures, and supplemental controls established

to provide an acceptable level of protection for sensitive data."

[FP039]

and configuration control.

$ Advanced Encryption Standard (AES)

(N) A future FIPS publication being developed by NIST to succeed

DES. Intended to specify an unclassified, publicly-disclosed,

symmetric encryption algorithm, available royalty-free worldwide.

$ adversary

(I) An entity that attacks, or is a threat to, a system.

$ aggregation

(I) A circumstance in which a collection of information items is

required to be classified at a higher security level than any of

the individual items that comprise it.

$ AH

See: Authentication Header

$ algorithm

(I) A finite set of step-by-step instructions for a problem-

solving or computation procedure, especially one that can be

implemented by a computer. (See: cryptographic algorithm.)

$ alias

(I) A name that an entity uses in place of its real name, usually

for the purpose of either anonymity or deception.

$ American National Standards Institute (ANSI)

(N) A private, not-for-profit association of users, manufacturers,

and other organizations, that administers U.S. private sector

voluntary standards.

treaty international standards organizations, ISO and, via the

U.S. National Committee (USNC), the International Electrotechnical

Commission (IEC).

$ anonymous

(I) The condition of having a name that is unknown or concealed.

(See: anonymous login.)

anonymity of users or other system entities, perhaps to preserve

their privacy or hide them from attack. To hide an entity's real

name, an alias may be used. For example, a financial institution

may assign an account number. Parties to a transaction can thus

remain relatively anonymous, but can also accept the transaction

as legitimate. Real names of the parties cannot be easily

determined by observers of the transaction, but an authorized

third party may be able to map an alias to a real name, such as by

presenting the institution with a court order. In other

applications, anonymous entities may be completely untraceable.

$ anonymous login

(I) An access control feature (or, rather, an access control

weakness) in many Internet hosts that enables users to gain access

to general-purpose or public services and resources on a host

(such as allowing any user to transfer data using File Transfer

Protocol) without having a pre-established, user-specific account

(i.e., user name and secret password).

the users are known, pre-registered entities that are individually

accountable for their actions. A user logs in using a special,

publicly known user name (e.g., "anonymous", "guest", or "FTP").

To use the public login name, the user is not required to know a

secret password and may not be required to input anything at all

except the name. In other cases, to complete the normal sequence

of steps in a login protocol, the system may require the user to

input a matching, publicly known password (such as "anonymous") or

may ask the user for an e-mail address or some other arbitrary

character string.

$ APOP

See: POP3 APOP.

$ archive

(I) (1.) Noun: A collection of data that is stored for a

relatively long period of time for historical and other purposes,

such as to support audit service, availability service, or system

integrity service. (See: backup.) (2.) Verb: To store data in such

a way. (See: back up.)

the signing occurs. The CA--the one that issued the certificate

containing the public key needed to verify that signature--may not

stay in operation that long. So every CA needs to provide for

long-term storage of the information needed to verify the

signatures of those to whom it issues certificates.

$ ARPANET

(N) Advanced Research Projects Agency Network, a pioneer packet-

switched network that was built in the early 1970s under contract

to the U.S. Government, led to the development of today's

Internet, and was decommissioned in June 1990.

$ ASN.1

See: Abstract Syntax Notation One.

$ association

(I) A cooperative relationship between system entities, usually

for the purpose of transferring information between them. (See:

security association.)

$ assurance

(I) (1.) An attribute of an information system that provides

grounds for having confidence that the system operates such that

the system security policy is enforced. (2.) A procedure that

ensures a system is developed and operated as intended by the

system's security policy.

$ assurance level

(I) Evaluation usage: A specific level on a hierarchical scale

representing successively increased confidence that a target of

evaluation adequately fulfills the requirements. (E.g., see:

TCSEC.)

$ asymmetric cryptography

(I) A modern branch of cryptography (popularly known as "public-

key cryptography") in which the algorithms employ a pair of keys

(a public key and a private key) and use a different component of

the pair for different steps of the algorithm. (See: key pair.)

equivalently strong symmetric ones. First, one key of the pair

does not need to be known by anyone but its owner; so it can more

easily be kept secret. Second, although the other key of the pair

is shared by all entities that use the algorithm, that key does

not need to be kept secret from other, non-using entities; so the

key distribution part of key management can be done more easily.

see: RSA), when Alice wants to ensure confidentiality for data she

sends to Bob, she encrypts the data with a public key provided by

Bob. Only Bob has the matching private key that is needed to

decrypt the data.

(e.g., see: DSA), when Alice wants to ensure data integrity or

provide authentication for data she sends to Bob, she uses her

private key to sign the data (i.e., create a digital signature

based on the data). To verify the signature, Bob uses the matching

public key that Alice has provided.

(e.g., see: Diffie-Hellman), Alice and Bob each send their own

public key to the other person. Then each uses their own private

key and the other's public key to compute the new key value.

$ attack

(I) An assault on system security that derives from an intelligent

threat, i.e., an intelligent act that is a deliberate attempt

(especially in the sense of a method or technique) to evade

security services and violate the security policy of a system.

(See: penetration, violation, vulnerability.)

- Active vs. passive: An "active attack" attempts to alter system

resources or affect their operation. A "passive attack"

attempts to learn or make use of information from the system

but does not affect system resources. (E.g., see: wiretapping.)

- Insider vs. outsider: An "inside attack" is an attack initiated

by an entity inside the security perimeter (an "insider"),

i.e., an entity that is authorized to access system resources

but uses them in a way not approved by those who granted the

authorization. An "outside attack" is initiated from outside

the perimeter, by an unauthorized or illegitimate user of the

system (an "outsider"). In the Internet, potential outside

attackers range from amateur pranksters to organized criminals,

international terrorists, and hostile governments.

as shown in the following diagram:

+ - - - - - - - - - - - - + + - - - - + + - - - - - - - - - - -+

An Attack: Counter- A System Resource:

i.e., A Threat Action measure Target of the Attack

+----------+ +-----------------+

Attacker <==================<=========

i.e., Passive Vulnerability

A Threat <=================><========>

Agent or Active +--------------+

+----------+ Attack VVV

Threat Consequences

+ - - - - - - - - - - - - + + - - - - + + - - - - - - - - - - -+

$ attribute authority

(I) A CA that issues attribute certificates.

(O) "An authority, trusted by the verifier to delegate privilege,

which issues attribute certificates." [FPDAM]

$ attribute certificate

(I) A digital certificate that binds a set of descriptive data

items, other than a public key, either directly to a subject name

or to the identifier of another certificate that is a public-key

certificate. [X509]

(O) "A set of attributes of a user together with some other

information, rendered unforgeable by the digital signature created

using the private key of the CA which issued it." [X509]

(O) "A data structure that includes some attribute values and

identification information about the owner of the attribute

certificate, all digitally signed by an Attribute Authority. This

authority's signature serves as the guarantee of the binding

between the attributes and their owner." [FPDAM]

value, along with information needed to perform certain

cryptographic functions. Other attributes of a subject, such as a

security clearance, may be certified in a separate kind of digital

certificate, called an attribute certificate. A subject may have

multiple attribute certificates associated with its name or with

each of its public-key certificates.

following situations:

- Different lifetimes: When the lifetime of an attribute binding

is shorter than that of the related public-key certificate, or

when it is desirable not to need to revoke a subject's public

key just to revoke an attribute.

- Different authorities: When the authority responsible for the

attributes is different than the one that issues the public-key

certificate for the subject. (There is no requirement that an

attribute certificate be issued by the same CA that issued the

associated public-key certificate.)

$ audit service

(I) A security service that records information needed to

establish accountability for system events and for the actions of

system entities that cause them. (See: security audit.)

$ audit trail

See: security audit trail.

$ AUTH

See: POP3 AUTH.

$ authentic signature

(I) A signature (particularly a digital signature) that can be

trusted because it can be verified. (See: validate vs. verify.)

$ authenticate

(I) Verify (i.e., establish the truth of) an identity claimed by

or for a system entity. (See: authentication.)

(D) In general English usage, this term usually means "to prove

genuine" (e.g., an art expert authenticates a Michelangelo

painting). But the recommended definition carries a much narrower

meaning. For example, to be precise, an ISD SHOULD NOT say "the

host authenticates each received datagram". Instead, the ISD

SHOULD say "the host authenticates the origin of each received

datagram". In most cases, we also can say "and verifies the

datagram's integrity", because that is usually implied. (See:

("relationship between data integrity service and authentication

services" under) data integrity service.)

(D) ISDs SHOULD NOT talk about authenticating a digital signature

or digital certificate. Instead, we "sign" and then "verify"

digital signatures, and we "issue" and then "validate" digital

certificates. (See: validate vs. verify.)

$ authentication

(I) The process of verifying an identity claimed by or for a

system entity. (See: authenticate, authentication exchange,

authentication information, credential, data origin

authentication, peer entity authentication.)

1. Identification step: Presenting an identifier to the security

system. (Identifiers should be assigned carefully, because

authenticated identities are the basis for other security

services, such as access control service.)

2. Verification step: Presenting or generating authentication

information that corroborates the binding between the entity

and the identifier. (See: verification.)

authentication services" under) data integrity service.

$ authentication code

(D) ISDs SHOULD NOT use this term as a synonym for any form of

checksum, whether cryptographic or not. The word "authentication"

is misleading because the mechanism involved usually serves a data

integrity function rather than an authentication function, and the

word "code" is misleading because it implies that either encoding

or encryption is involved or that the term refers to computer

software. (See: message authentication code.)

$ authentication exchange

(I) A mechanism to verify the identity of an entity by means of

information exchange.

(O) "A mechanism intended to ensure the identity of an entity by

means of information exchange." [I7498 Part 2]

$ Authentication Header (AH)

(I) An Internet IPsec protocol [R2402] designed to provide

connectionless data integrity service and data origin

authentication service for IP datagrams, and (optionally) to

provide protection against replay attacks.

security association is established. AH authenticates upper-layer

protocol data units and as much of the IP header as possible.

However, some IP header fields may change in transit, and the

value of these fields, when the packet arrives at the receiver,

may not be predictable by the sender. Thus, the values of such

fields cannot be protected end-to-end by AH; protection of the IP

header by AH is only partial when such fields are present.

protocol, or in a nested fashion with tunneling. Security services

can be provided between a pair of communicating hosts, between a

pair of communicating security gateways, or between a host and a

gateway. ESP can provide the same security services as AH, and ESP

can also provide data confidentiality service. The main difference

between authentication services provided by ESP and AH is the

extent of the coverage; ESP does not protect IP header fields

unless they are encapsulated by AH.

$ authentication information

(I) Information used to verify an identity claimed by or for an

entity. (See: authentication, credential.)

one of the following:

- Something the entity knows. (See: password).

- Something the entity possesses. (See: token.)

- Something the entity is. (See: biometric authentication.)

$ authentication service

(I) A security service that verifies an identity claimed by or for

an entity. (See: authentication.)

service: data origin authentication service and peer entity

authentication service.

$ authenticity

(I) The property of being genuine and able to be verified and be

trusted. (See: authenticate, authentication, validate vs. verify)

$ authority

(D) "An entity, responsible for the issuance of certificates."

[FPDAM]

ORA, or similar terms, because it may cause confusion. Instead,

use the full term at the first instance of usage and then, if it

is necessary to shorten text, use the style of abbreviation

defined in this Glossary.

because the definition is ambiguous with regard to whether the

entity actually issues certificates (e.g., attribute authority or

certification authority) or just has accountability for processes

that precede or follow signing (e.g., registration authority).

(See: issue.)

$ authority certificate

(D) "A certificate issued to an authority (e.g. either to a

certification authority or to an attribute authority)." [FPDAM]

(See: authority.)

ambiguous with regard to which specific types of PKI entities they

address.

$ authority revocation list (ARL)

(I) A data structure that enumerates digital certificates that

were issued to CAs but have been invalidated by their issuer prior

to when they were scheduled to expire. (See: certificate

expiration, X.509 authority revocation list.)

(O) "A revocation list containing a list of public-key

certificates issued to authorities, which are no longer considered

valid by the certificate issuer." [FPDAM]

$ authorization

$ authorize

(I) (1.) An "authorization" is a right or a permission that is

granted to a system entity to access a system resource. (2.) An

"authorization process" is a procedure for granting such rights.

(3.) To "authorize" means to grant such a right or permission.

(See: privilege.)

(O) SET usage: "The process by which a properly appointed person

or persons grants permission to perform some action on behalf of

an organization. This process assesses transaction risk, confirms

that a given transaction does not raise the account holder's deBT

above the account's credit limit, and reserves the specified

amount of credit. (When a merchant obtains authorization, payment

for the authorized amount is guaranteed--provided, of course, that

the merchant followed the rules associated with the authorization

process.)" [SET2]

$ automated information system

(I) An organized assembly of resources and procedures--i.e.,

computing and communications equipment and services, with their

supporting facilities and personnel--that collect, record,

process, store, transport, retrieve, or display information to

accomplish a specified set of functions.

$ availability

(I) The property of a system or a system resource being accessible

and usable upon demand by an authorized system entity, according

to performance specifications for the system; i.e., a system is

available if it provides services according to the system design

whenever users request them. (See: critical, denial of service,

reliability, survivability.)

(O) "The property of being accessible and usable upon demand by an

authorized entity." [I7498 Part 2]

$ availability service

(I) A security service that protects a system to ensure its

availability.

of-service attacks. It depends on proper management and control of

system resources, and thus depends on access control service and

other security services.

$ back door

(I) A hardware or software mechanism that (a) provides access to a

system and its resources by other than the usual procedure, (b)

was deliberately left in place by the system's designers or

maintainers, and (c) usually is not publicly known. (See: trap

door.)

normal login. Such access paths do not necessarily have malicious

intent; e.g., operating systems sometimes are shipped by the

manufacturer with privileged accounts intended for use by field

service technicians or the vendor's maintenance programmers. (See:

trap door.)

$ back up vs. backup

(I) Verb "back up": To store data for the purpose of creating a

backup copy. (See: archive.)

(I) Noun/adjective "backup": (1.) A reserve copy of data that is

stored separately from the original, for use if the original

becomes lost or damaged. (See: archive.) (2.) Alternate means to

permit performance of system functions despite a disaster to

system resources. (See: contingency plan.)

$ baggage

(D) ISDs SHOULD NOT use this term to describe a data element

except when stated as "SET(trademark) baggage" with the following

meaning:

(O) SET usage: An "opaque encrypted tuple, which is included in a

SET message but appended as external data to the PKCS encapsulated

data. This avoids superencryption of the previously encrypted

tuple, but guarantees linkage with the PKCS portion of the

message." [SET2]

$ bandwidth

(I) Commonly used to mean the capacity of a communication channel

to pass data through the channel in a given amount of time.

Usually expressed in bits per second.

$ bank identification number (BIN)

(N) The digits of a credit card number that identify the issuing

bank. (See: primary account number.)

(O) SET usage: The first six digits of a primary account number.

$ Basic Encoding Rules (BER)

(I) A standard for representing ASN.1 data types as strings of

octets. [X690] (See: Distinguished Encoding Rules.)

$ bastion host

(I) A strongly protected computer that is in a network protected

by a firewall (or is part of a firewall) and is the only host (or

one of only a few hosts) in the network that can be directly

accessed from networks on the other side of the firewall.

from the outside network to reaching just one host, the bastion

host, which usually is part of the firewall. Since only this one

host can be directly attacked, only this one host needs to be very

strongly protected, so security can be maintained more easily and

less expensively. However, to allow legitimate internal and

external users to access application resources through the

firewall, higher layer protocols and services need to be relayed

and forwarded by the bastion host. Some services (e.g., DNS and

SMTP) have forwarding built in; other services (e.g., TELNET and

FTP) require a proxy server on the bastion host.

$ BCA

See: brand certification authority.

$ BCI

See: brand CRL identifier.

$ Bell-LaPadula Model

(N) A formal, mathematical, state-transition model of security

policy for multilevel-secure computer systems. [Bell]

subjects and a set of objects. To determine whether or not a

subject is authorized for a particular access mode on an object,

the clearance of the subject is compared to the classification of

the object. The model defines the notion of a "secure state", in

which the only permitted access modes of subjects to objects are

in accordance with a specified security policy. It is proven that

each state transition preserves security by moving from secure

state to secure state, thereby proving that the system is secure.

rules, including the following:

- "Confinement property" (also called "*-property", pronounced

"star property"): A subject has write access to an object only

if classification of the object dominates the clearance of the

subject.

- "Simple security property": A subject has read access to an

object only if the clearance of the subject dominates the

classification of the object.

- "Tranquillity property": The classification of an object does

not change while the object is being processed by the system.

$ BER

See: Basic Encoding Rules.

$ beyond A1

(O) (1.) Formally, a level of security assurance that is beyond

the highest level of criteria specified by the TCSEC. (2.)

Informally, a level of trust so high that it cannot be provided or

verified by currently available assurance methods, and

particularly not by currently available formal methods.

$ BIN

See: bank identification number.

$ bind

(I) To inseparably associate by applying some mechanism, such as

when a CA uses a digital signature to bind together a subject and

a public key in a public-key certificate.

$ biometric authentication

(I) A method of generating authentication information for a person

by digitizing measurements of a physical characteristic, such as a

fingerprint, a hand shape, a retina pattern, a speech pattern

(voiceprint), or handwriting.

$ bit

(I) The smallest unit of information storage; a contraction of the

term "binary digit"; one of two symbols--"0" (zero) and "1" (one)

--that are used to represent binary numbers.

$ BLACK

(I) Designation for information system equipment or facilities

that handle (and for data that contains) only ciphertext (or,

depending on the context, only unclassified information), and for

such data itself. This term derives from U.S. Government COMSEC

terminology. (See: RED, RED/BLACK separation.)

$ block cipher

(I) An encryption algorithm that breaks plaintext into fixed-size

segments and uses the same key to transform each plaintext segment

into a fixed-size segment of ciphertext. (See: mode, stream

cipher.)

a block cipher can be adapted to have a different external

interface, such as that of a stream cipher, by using a mode of

operation to "package" the basic algorithm.

$ Blowfish

(N) A symmetric block cipher with variable-length key (32 to 448

bits) designed in 1993 by Bruce Schneier as an unpatented,

license-free, royalty-free replacement for DES or IDEA. [Schn]

$ brand

(I) A distinctive mark or name that identifies a product or

business entity.

(O) SET usage: The name of a payment card. Financial institutions

and other companies have founded payment card brands, protect and

advertise the brands, establish and enforce rules for use and

acceptance of their payment cards, and provide networks to

interconnect the financial institutions. These brands combine the

roles of issuer and acquirer in interactions with cardholders and

merchants. [SET1]

$ brand certification authority (BCA)

(O) SET usage: A CA owned by a payment card brand, such as

MasterCard, Visa, or American Express. [SET2] (See: certification

hierarchy, SET.)

$ brand CRL identifier (BCI)

(O) SET usage: A digitally signed list, issued by a BCA, of the

names of CAs for which CRLs need to be processed when verifying

signatures in SET messages. [SET2]

$ break

(I) Cryptographic usage: To successfully perform cryptanalysis and

thus succeed in decrypting data or performing some other

cryptographic function, without initially having knowledge of the

key that the function requires. (This term applies to encrypted

data or, more generally, to a cryptographic algorithm or

cryptographic system.)

$ bridge

(I) A computer that is a gateway between two networks (usually two

LANs) at OSI layer 2. (See: router.)

$ British Standard 7799

(N) Part 1 is a standard code of practice and provides guidance on

how to secure an information system. Part 2 specifies the

management framework, objectives, and control requirements for

information security management systems [B7799]. The certification

scheme works like ISO 9000. It is in use in the UK, the

Netherlands, Australia, and New Zealand and might be proposed as

an ISO standard or adapted to be part of the Common Criteria.

$ browser

(I) An client computer program that can retrieve and display

information from servers on the World Wide Web.

Microsoft's Explorer.

$ brute force

(I) A cryptanalysis technique or other kind of attack method

involving an exhaustive procedure that tries all possibilities,

one-by-one.

the decryption algorithm, a brute force technique to finding the

original plaintext is to decrypt the message with every possible

key.

$ BS7799

See: British Standard 7799.

$ byte

(I) A fundamental unit of computer storage; the smallest

addressable unit in a computer's architecture. Usually holds one

character of information and, today, usually means eight bits.

(See: octet.)

"byte" almost always means "octet" today, bytes had other sizes

(e.g., six bits, nine bits) in earlier computer architectures.

$ CA

See: certification authority.

$ CA certificate

(I) "A [digital] certificate for one CA issued by another CA."

[X509]

digital certificates. A v3 X.509 public-key certificate may have a

"basicConstraints" extension containing a "cA" value that

specifically "indicates whether or not the public key may be used

to verify certificate signatures."

$ call back

(I) An authentication technique for terminals that remotely access

a computer via telephone lines. The host system disconnects the

caller and then calls back on a telephone number that was

previously authorized for that terminal.

$ capability

(I) A token, usually an unforgeable data value (sometimes called a

"ticket") that gives the bearer or holder the right to access a

system resource. Possession of the token is accepted by a system

as proof that the holder has been authorized to access the

resource named or indicated by the token. (See: access control

list, credential, digital certificate.)

(See: attribute certificate.)

$ CAPI

See: cryptographic application programming interface.

$ CAPSTONE chip

(N) An integrated circuit (the Mykotronx, Inc. MYK-82) with a Type

II cryptographic processor that implements SKIPJACK, KEA, DSA,

SHA, and basic mathematical functions to support asymmetric

cryptography, and includes the key escrow feature of the CLIPPER

chip. (See: FORTEZZA card.)

$ card

See: cryptographic card, FORTEZZA card, payment card, PC card,

smart card, token.

$ card backup

See: token backup.

$ card copy

See: token copy.

$ card restore

See: token restore.

$ cardholder

(I) An entity that has been issued a card.

(O) SET usage: "The holder of a valid payment card account and

user of software supporting electronic commerce." [SET2] A

cardholder is issued a payment card by an issuer. SET ensures that

in the cardholder's interactions with merchants, the payment card

account information remains confidential. [SET1]

$ cardholder certificate

(O) SET usage: A digital certificate that is issued to a

cardholder upon approval of the cardholder's issuing financial

institution and that is transmitted to merchants with purchase

requests and encrypted payment instructions, carrying assurance

that the account number has been validated by the issuing

financial institution and cannot be altered by a third party.

[SET1]

$ cardholder certification authority (CCA)

(O) SET usage: A CA responsible for issuing digital certificates

to cardholders and operated on behalf of a payment card brand, an

issuer, or another party according to brand rules. A CCA maintains

relationships with card issuers to allow for the verification of

cardholder accounts. A CCA does not issue a CRL but does

distribute CRLs issued by root CAs, brand CAs, geopolitical CAs,

and payment gateway CAs. [SET2]

$ CAST

(N) A design procedure for symmetric encryption algorithms, and a

resulting family of algorithms, invented by C.A. (Carlisle Adams)

and S.T. (Stafford Tavares). [R2144, R2612]

$ category

(I) A grouping of sensitive information items to which a non-

hierarchical restrictive security label is applied to increase

protection of the data. (See: compartment.)

$ CAW

See: certification authority workstation.

$ CBC

See: cipher block chaining.

$ CCA

See: cardholder certification authority.

$ CCITT

(N) Acronym for French translation of International Telephone and

Telegraph Consultative Committee. Now renamed ITU-T.

$ CERT

See: computer emergency response team.

$ certificate

(I) General English usage: A document that attests to the truth of

something or the ownership of something.

$ certificate authority

(D) ISDs SHOULD NOT use this term because it looks like sloppy use

of "certification authority", which is the term standardized by

X.509.

$ certificate chain

(D) ISDs SHOULD NOT use this term because it duplicates the

meaning of a standardized term. Instead, use "certification path".

$ certificate chain validation

(D) ISDs SHOULD NOT use this term because it duplicates the

meaning of standardized terms and mixes concepts in a potentially

misleading way. Instead, use "certificate validation" or "path

validation", depending on what is meant. (See: validate vs.

verify.)

$ certificate creation

(I) The act or process by which a CA sets the values of a digital

certificate's data fields and signs it. (See: issue.)

$ certificate expiration

(I) The event that occurs when a certificate ceases to be valid

because its assigned lifetime has been exceeded. (See: certificate

revocation, validity period.)

$ certificate extension

See: extension.

$ certificate holder

(D) ISDs SHOULD NOT use this term as a synonym for the subject of

a digital certificate because the term is potentially ambiguous.

For example, the term could also refer to a system entity, such as

a repository, that simply has possession of a copy of the

certificate. (See: certificate owner.)

$ certificate management

(I) The functions that a CA may perform during the life cycle of a

digital certificate, including the following:

- Acquire and verify data items to bind into the certificate.

- Encode and sign the certificate.

- Store the certificate in a Directory or repository.

- Renew, rekey, and update the certificate.

- Revoke the certificate and issue a CRL.

(See: archive management, certificate management, key management,

security architecture, token management.)

$ certificate owner

(D) ISDs SHOULD NOT use this term as a synonym for the subject of

a digital certificate because the term is potentially ambiguous.

For example, the term could also refer to a system entity, such as

a corporation, that has acquired a certificate to operate some

other entity, such as a Web server. (See: certificate holder.)

$ certificate policy

(I) "A named set of rules that indicates the applicability of a

certificate to a particular community and/or class of application

with common security requirements." [X509] (See: certification

practice statement.)

whether a certificate should be trusted in a particular

application. "For example, a particular certificate policy might

indicate applicability of a type of certificate for the

authentication of electronic data interchange transactions for the

trading goods within a given price range." [R2527]

"certificatePolicies" extension that lists certificate policies,

recognized by the issuing CA, that apply to the certificate and

govern its use. Each policy is denoted by an object identifier and

may optionally have certificate policy qualifiers.

certificate policy, that of the SET root CA. SET uses certificate

policy qualifiers to point to the actual policy statement and to

add qualifying policies to the root policy. (See: SET qualifier.)

$ certificate policy qualifier

(I) Information that pertains to a certificate policy and is

included in a "certificatePolicies" extension in a v3 X.509

public-key certificate.

$ certificate reactivation

(I) The act or process by which a digital certificate, which a CA

has designated for revocation but not yet listed on a CRL, is

returned to the valid state.

$ certificate rekey

(I) The act or process by which an existing public-key certificate

has its public key value changed by issuing a new certificate with

a different (usually new) public key. (See: certificate renewal,

certificate update, rekey.)

that the subject stays the same and a new public key is bound to

that subject. Other changes are made, and the old certificate is

revoked, only as required by the PKI and CPS in support of the

rekey. If changes go beyond that, the process is a "certificate

update".

(O) MISSI usage: To rekey a MISSI X.509 public-key certificate

means that the issuing authority creates a new certificate that is

identical to the old one, except the new one has a new, different

KEA key; or a new, different DSS key; or new, different KEA and

DSS keys. The new certificate also has a different serial number

and may have a different validity period. A new key creation date

and maximum key lifetime period are assigned to each newly

generated key. If a new KEA key is generated, that key is assigned

a new KMID. The old certificate remains valid until it expires,

but may not be further renewed, rekeyed, or updated.

$ certificate renewal

(I) The act or process by which the validity of the data binding

asserted by an existing public-key certificate is extended in time

by issuing a new certificate. (See: certificate rekey, certificate

update.)

validity period is extended (and, of course, a new serial number

is assigned) but the binding of the public key to the subject and

to other data items stays the same. The other data items are

changed, and the old certificate is revoked, only as required by

the PKI and CPS to support the renewal. If changes go beyond that,

the process is a "certificate rekey" or "certificate update".

$ certificate request

(D) ISDs SHOULD NOT use this term because it looks like imprecise

use of a term standardized by PKCS #10 and used in PKIX. Instead,

use the standard term, "certification request".

$ certificate revocation

(I) The event that occurs when a CA declares that a previously

valid digital certificate issued by that CA has become invalid;

usually stated with a revocation date.

users by issuing a CRL that mentions the certificate. Revocation

and listing on a CRL is only necessary before certificate

expiration.

$ certificate revocation list (CRL)

(I) A data structure that enumerates digital certificates that

have been invalidated by their issuer prior to when they were

scheduled to expire. (See: certificate expiration, X.509

certificate revocation list.)

(O) "A signed list indicating a set of certificates that are no

longer considered valid by the certificate issuer. After a

certificate appears on a CRL, it is deleted from a subsequent CRL

after the certificate's expiry. CRLs may be used to identify

revoked public-key certificates or attribute certificates and may

represent revocation of certificates issued to authorities or to

users. The term CRL is also commonly used as a generic term

applying to all the different types of revocation lists, including

CRLs, ARLs, ACRLs, etc." [FPDAM]

$ certificate revocation tree

(I) A mechanism for distributing notice of certificate

revocations; uses a tree of hash results that is signed by the

tree's issuer. Offers an alternative to issuing a CRL, but is not

supported in X.509. (See: certificate status responder.)

$ certificate serial number

(I) An integer value that (a) is associated with, and may be

carried in, a digital certificate; (b) is assigned to the

certificate by the certificate's issuer; and (c) is unique among

all the certificates produced by that issuer.

(O) "An integer value, unique within the issuing CA, which is

unambiguously associated with a certificate issued by that CA."

[X509]

$ certificate status responder

(N) FPKI usage: A trusted on-line server that acts for a CA to

provide authenticated certificate status information to

certificate users. [FPKI] Offers an alternative to issuing a CRL,

but is not supported in X.509. (See: certificate revocation tree.)

$ certificate update

(I) The act or process by which non-key data items bound in an

existing public-key certificate, especially authorizations granted

to the subject, are changed by issuing a new certificate. (See:

certificate rekey, certificate renewal.)

process is that fundamental changes are made in the data that is

bound to the public key, such that it is necessary to revoke the

old certificate. (Otherwise, the process is only a "certificate

rekey" or "certificate renewal".)

$ certificate user

(I) A system entity that depends on the validity of information

(such as another entity's public key value) provided by a digital

certificate. (See: relying party.)

(O) "An entity that needs to know, with certainty, the public key

of another entity." [X509]

a device or process under the control of a human or an

organization.

(D) ISDs SHOULD NOT use this term as a synonym for the "subject"

of a certificate.

$ certificate validation

(I) An act or process by which a certificate user establishes that

the assertions made by a digital certificate can be trusted. (See:

valid certificate, validate vs. verify.)

(O) "The process of ensuring that a certificate is valid including

possibly the construction and processing of a certification path,

and ensuring that all certificates in that path have not expired

or been revoked." [FPDAM]

certificate is properly formed and signed and currently in force:

- Checks the signature: Employs the issuer's public key to verify

the digital signature of the CA who issued the certificate in

question. If the verifier obtains the issuer's public key from

the issuer's own public-key certificate, that certificate

should be validated, too. That validation may lead to yet

another certificate to be validated, and so on. Thus, in

general, certificate validation involves discovering and

validating a certification path.

- Checks the syntax and semantics: Parses the certificate's

syntax and interprets its semantics, applying rules specified

for and by its data fields, such as for critical extensions in

an X.509 certificate.

- Checks currency and revocation: Verifies that the certificate

is currently in force by checking that the current date and

time are within the validity period (if that is specified in

the certificate) and that the certificate is not listed on a

CRL or otherwise announced as invalid. (CRLs themselves require

a similar validation process.)

$ certification

(I) Information system usage: Technical evaluation (usually made

in support of an accreditation action) of an information system's

security features and other safeguards to establish the extent to

which the system's design and implementation meet specified

security requirements. [FP102] (See: accreditation.)

(I) Digital certificate usage: The act or process of vouching for

the truth and accuracy of the binding between data items in a

certificate. (See: certify.)

(I) Public key usage: The act or process of vouching for the

ownership of a public key by issuing a public-key certificate that

binds the key to the name of the entity that possesses the

matching private key. In addition to binding a key to a name, a

public-key certificate may bind those items to other restrictive

or explanatory data items. (See: X.509 public-key certificate.)

(O) SET usage: "The process of ascertaining that a set of

requirements or criteria has been fulfilled and attesting to that

fact to others, usually with some written instrument. A system

that has been inspected and evaluated as fully compliant with the

SET protocol by duly authorized parties and process would be said

to have been certified compliant." [SET2]

$ certification authority (CA)

(I) An entity that issues digital certificates (especially X.509

certificates) and vouches for the binding between the data items

in a certificate.

(O) "An authority trusted by one or more users to create and

assign certificates. Optionally, the certification authority may

create the user's keys." [X509]

provided by a certificate. Thus, a CA should be someone that

certificate users trust, and usually holds an official position

created and granted power by a government, a corporation, or some

other organization. A CA is responsible for managing the life

cycle of certificates (see: certificate management) and, depending

on the type of certificate and the CPS that applies, may be

responsible for the life cycle of key pairs associated with the

certificates (see: key management).

$ certification authority workstation (CAW)

(I) A computer system that enables a CA to issue digital

certificates and supports other certificate management functions

as required.

$ certification hierarchy

(I) A tree-structured (loop-free) topology of relationships among

CAs and the entities to whom the CAs issue public-key

certificates. (See: hierarchical PKI.)

the hierarchy. (See: root, top CA.) The top CA may issue public-

key certificates to one or more additional CAs that form the

second highest level. Each of these CAs may issue certificates to

more CAs at the third highest level, and so on. The CAs at the

second-lowest of the hierarchy issue certificates only to non-CA

entities, called "end entities" that form the lowest level. (See:

end entity.) Thus, all certification paths begin at the top CA and

descend through zero or more levels of other CAs. All certificate

users base path validations on the top CA's public key.

(O) MISSI usage: A MISSI certification hierarchy has three or four

levels of CAs:

- A CA at the highest level, the top CA, is a "policy approving

authority".

- A CA at the second-highest level is a "policy creation

authority".

- A CA at the third-highest level is a local authority called a

"certification authority".

- A CA at the fourth-highest (optional) level is a "subordinate

certification authority".

(O) PEM usage: A PEM certification hierarchy has three levels of

CAs [R1422]:

- The highest level is the "Internet Policy Registration

Authority".

- A CA at the second-highest level is a "policy certification

authority".

- A CA at the third-highest level is a "certification authority".

(O) SET usage: A SET certification hierarchy has three or four

levels of CAs:

- The highest level is a "SET root CA".

- A CA at the second-highest level is a "brand certification

authority".

- A CA at the third-highest (optional) level is a "geopolitical

certification authority".

- A CA at the fourth-highest level is a "cardholder CA", a

"merchant CA", or a "payment gateway CA".

$ certification path

(I) An ordered sequence of public-key certificates (or a sequence

of public-key certificates followed by one attribute certificate)

that enables a certificate user to verify the signature on the

last certificate in the path, and thus enables the user to obtain

a certified public key (or certified attributes) of the entity

that is the subject of that last certificate. (See: certificate

validation, valid certificate.)

(O) "An ordered sequence of certificates of objects in the [X.500

Directory Information Tree] which, together with the public key of

the initial object in the path, can be processed to obtain that of

the final object in the path." [X509, R2527]

particular user to obtain the public key of another." [X509] The

list is "linked" in the sense that the digital signature of each

certificate (except the first) is verified by the public key

contained in the preceding certificate; i.e., the private key used

to sign a certificate and the public key contained in the

preceding certificate form a key pair owned by the entity that

signed.

"particular" points out that a certification path that can be

validated by one certificate user might not be able to be

validated by another. That is because either the first certificate

should be a trusted certificate (it might be a root certificate)

or the signature on the first certificate should be verified by a

trusted key (it might be a root key), but such trust is defined

relative to each user, not absolutely for all users.

$ certification policy

(D) ISDs SHOULD NOT use this term. Instead, use either

"certificate policy" or "certification practice statement",

depending on what is meant.

$ certification practice statement (CPS)

(I) "A statement of the practices which a certification authority

employs in issuing certificates." [ABA96, R2527] (See: certificate

policy.)

certificate user to decide whether a certificate issued by a

particular CA can be trusted enough to use in a particular

application. A CPS may be (a) a declaration by a CA of the details

of the system and practices it employs in its certificate

management operations, (b) part of a contract between the CA and

an entity to whom a certificate is issued, (c) a statute or

regulation applicable to the CA, or (d) a combination of these

types involving multiple documents. [ABA]

a certificate policy. A CPS applies to a particular CA or CA

community, while a certificate policy applies across CAs or

communities. A CA with a single CPS may support multiple

certificate policies, which may be used for different application

purposes or by different user communities. Multiple CAs, each with

a different CPS, may support the same certificate policy. [R2527]

$ certification request

(I) A algorithm-independent transaction format, defined by PCKS

#10 and used in PKIX, that contains a DN, a public key, and

optionally a set of attributes, collectively signed by the entity

requesting certification, and sent to a CA, which transforms the

request to an X.509 public-key certificate or another type of

certificate.

$ certify

1. (I) Issue a digital certificate and thus vouch for the truth,

accuracy, and binding between data items in the certificate (e.g.,

see: X.509 public key certificate), such as the identity of the

certificate's subject and the ownership of a public key. (See:

certification.)

certificate that vouches for the binding between the certificate's

subject and the key.

2. (I) The act by which a CA employs measures to verify the truth,

accuracy, and binding between data items in a digital certificate.

included in the CA's CPS.

$ CFB

See: cipher feedback.

$ Challenge Handshake Authentication Protocol (CHAP)

(I) A peer entity authentication method for PPP, using a randomly-

generated challenge and requiring a matching response that depends

on a cryptographic hash of the challenge and a secret key. [R1994]

(See: challenge-response, PAP.)

$ challenge-response

(I) An authentication process that verifies an identity by

requiring correct authentication information to be provided in

response to a challenge. In a computer system, the authentication

information is usually a value that is required to be computed in

response to an unpredictable challenge value.

$ Challenge-Response Authentication Mechanism (CRAM)

(I) IMAP4 usage: A mechanism [R2195], intended for use with IMAP4

AUTHENTICATE, by which an IMAP4 client uses a keyed hash [R2104]

to authenticate itself to an IMAP4 server. (See: POP3 APOP.)

to the client. The client replies with the client's name and the

hash result of applying MD5 to a string formed from concatenating

the timestamp with a shared secret that is known only to the

client and the server.

$ channel

(I) An information transfer path within a system. (See: covert

channel.)

$ CHAP

See: Challenge Handshake Authentication Protocol.

$ checksum

(I) A value that (a) is computed by a function that is dependent

on the contents of a data object and (b) is stored or transmitted

together with the object, for the purpose of detecting changes in

the data. (See: cyclic redundancy check, data integrity service,

error detection code, hash, keyed hash, protected checksum.)

entity that later uses the data can compute a checksum and compare

it with the checksum that was stored or transmitted with the

object.

mechanisms) to detect accidental changes in data. However, active

wiretapping that changes data could also change an accompanying

checksum to match the changed data. Thus, some checksum functions

by themselves are not good countermeasures for active attacks. To

protect against active attacks, the checksum function needs to be

well-chosen (see: cryptographic hash), and the checksum result

needs to be cryptographically protected (see: digital signature,

keyed hash).

$ chosen-ciphertext attack

(I) A cryptanalysis technique in which the analyst tries to

determine the key from knowledge of plaintext that corresponds to

ciphertext selected (i.e., dictated) by the analyst.

$ chosen-plaintext attack

(I) A cryptanalysis technique in which the analyst tries to

determine the key from knowledge of ciphertext that corresponds to

plaintext selected (i.e., dictated) by the analyst.

$ CIAC

See: Computer Incident Advisory Capability.

$ CIK

See: cryptographic ignition key.

$ cipher

(I) A cryptographic algorithm for encryption and decryption.

$ cipher block chaining (CBC)

(I) An block cipher mode that enhances electronic codebook mode by

chaining together blocks of ciphertext it produces. [FP081] (See:

[R1829], [R2451].)

algorithm's ciphertext output block with the next plaintext block

to form the next input block for the algorithm.

$ cipher feedback (CFB)

(I) An block cipher mode that enhances electronic code book mode

by chaining together the blocks of ciphertext it produces and

operating on plaintext segments of variable length less than or

equal to the block length. [FP081]

ciphertext segment as the algorithm's input (i.e., by "feeding

back" the ciphertext) to generate an output block, and then

combining (exclusive OR-ing) that output block with the next

plaintext segment (block length or less) to form the next

ciphertext segment.

$ ciphertext

(I) Data that has been transformed by encryption so that its

semantic information content (i.e., its meaning) is no longer

intelligible or directly available. (See: cleartext, plaintext.)

(O) "Data produced through the use of encipherment. The semantic

content of the resulting data is not available." [I7498 Part 2]

$ ciphertext-only attack

(I) A cryptanalysis technique in which the analyst tries to

determine the key solely from knowledge of intercepted ciphertext

(although the analyst may also know other clues, such as the

cryptographic algorithm, the language in which the plaintext was

written, the subject matter of the plaintext, and some probable

plaintext words.)

$ CIPSO

See: Common IP Security Option.

$ CKL

See: compromised key list.

$ class 2, 3, 4, or 5

(O) U.S. Department of Defense usage: Levels of PKI assurance

based on risk and value of information to be protected [DOD3]:

- Class 2: For handling low-value information (unclassified, not

mission-critical, or low monetary value) or protection of

system-high information in low- to medium-risk environment.

- Class 3: For handling medium-value information in low- to

medium-risk environment. Typically requires identification of a

system entity as a legal person, rather than merely a member of

an organization.

- Class 4: For handling medium- to high-value information in any

environment. Typically requires identification of an entity as

a legal person, rather than merely a member of an organization,

and a cryptographic hardware token for protection of keying

material.

- Class 5: For handling high-value information in a high-risk

environment.

$ classification

$ classification level

(I) (1.) A grouping of classified information to which a

hierarchical, restrictive security label is applied to increase

protection of the data. (2.) The level of protection that is

required to be applied to that information. (See: security level.)

$ classified

(I) Refers to information (stored or conveyed, in any form) that

is formally required by a security policy to be given data

confidentiality service and to be marked with a security label

(which in some cases might be implicit) to indicate its protected

status. (See: unclassified.)

military, although the concept underlying the term also applies

outside government. In the U.S. Department of Defense, for

example, it means information that has been determined pursuant to

Executive Order 12958 ("Classified National Security Information",

20 April 1995) or any predecessor order to require protection

against unauthorized disclosure and is marked to indicate its

classified status when in documentary form.

$ clean system

(I) A computer system in which the operating system and

application system software and files have just been freshly

installed from trusted software distribution media.

$ clearance

See: security clearance.

$ clearance level

(I) The security level of information to which a security

clearance authorizes a person to have access.

$ cleartext

(I) Data in which the semantic information content (i.e., the

meaning) is intelligible or is directly available. (See:

plaintext.)

(O) "Intelligible data, the semantic content of which is

available." [I7498 Part 2]

(D) ISDs SHOULD NOT use this term as a synonym for "plaintext",

the input to an encryption operation, because the plaintext input

to encryption may itself be ciphertext that was output from

another operation. (See: superencryption.)

$ client

(I) A system entity that requests and uses a service provided by

another system entity, called a "server". (See: server.)

makes the request on behalf of a human user. In some cases, the

server may itself be a client of some other server.

$ CLIPPER chip

(N) The Mykotronx, Inc. MYK-82, an integrated microcircuit with a

cryptographic processor that implements the SKIPJACK encryption

algorithm and supports key escrow. (See: CAPSTONE, Escrowed

Encryption Standard.)

common to all chips that protects the unique serial number of the

chip, and a second SKIPJACK key unique to the chip that protects

all data encrypted by the chip. The second key is escrowed as

split key components held by NIST and the U.S. Treasury

Department.

$ closed security environment

(O) U.S. Department of Defense usage: A system environment that

meets both of the following conditions: (a) Application developers

(including maintainers) have sufficient clearances and

authorizations to provide an acceptable presumption that they have

not introduced malicious logic. (b) Configuration control provides

sufficient assurance that system applications and the equipment

they run on are protected against the introduction of malicious

logic prior to and during the operation of applications. [NCS04]

(See: open security environment.)

$ code

(I) noun: A system of symbols used to represent information, which

might originally have some other representation. (See: encode.)

(D) ISDs SHOULD NOT use this term as synonym for the following:

(a) "cipher", "hash", or other words that mean "a cryptographic

algorithm"; (b) "ciphertext"; or (c) "encrypt", "hash", or other

words that refer to applying a cryptographic algorithm.

(D) ISDs SHOULD NOT this word as an abbreviation for the following

terms: country code, cyclic redundancy code, Data Authentication

Code, error detection code, Message Authentication Code, object

code, or source code. To avoid misunderstanding, use the fully

qualified term, at least at the point of first usage.

$ color change

(I) In a system that is being operated in periods processing mode,

the act of purging all information from one processing period and

then changing over to the next processing period.

$ Common Criteria

$ Common Criteria for Information Technology Security

(N) "The Common Criteria" is a standard for evaluating information

technology products and systems, such as operating systems,

computer networks, distributed systems, and applications. It

states requirements for security functions and for assurance

measures. [CCIB]

and the United States (NIST and NSA) began developing this

standard in 1993, based on the European ITSEC, the Canadian

Trusted Computer Product Evaluation Criteria (CTCPEC), and the

U.S. "Federal Criteria for Information Technology Security" (FC)

and its precursor, the TCSEC. Work was done in cooperation with

ISO/IEC Joint Technical Committee 1 (Information Technology),

Subcommittee 27 (Security Techniques), Working Group 3 (Security

Criteria). Version 2.1 of the Criteria is equivalent to ISO's

International Standard 15408 [I15408]. The U.S. Government intends

that this standard eventually will supersede both the TCSEC and

FIPS PUB 140-1. (See: NIAP.)

and availability and may apply to other ASPects of security. It

focuses on threats to information arising from human activities,

malicious or otherwise, but may apply to non-human threats. It

applies to security measures implemented in hardware, firmware, or

software. It does not apply to (a) administrative security not

related directly to technical security, (b) technical physical

aspects of security such as electromagnetic emanation control, (c)

evaluation methodology or administrative and legal framework under

which the criteria may be applied, (d) procedures for use of

evaluation results, or (e) assessment of inherent qualities of

cryptographic algorithms.

$ Common IP Security Option (CIPSO)

See: (secondary definition under) Internet Protocol Security

Option.

$ common name

(I) A character string that (a) may be a part of the X.500 DN of a

Directory object ("commonName" attribute), (b) is a (possibly

ambiguous) name by which the object is commonly known in some

limited scope (such as an organization), and (c) conforms to the

naming conventions of the country or culture with which it is

associated. [X520] (See: ("subject" and "issuer" under) X.509

public-key certificate.)

"12-th Floor Laser Printer".

$ communication security (COMSEC)

(I) Measures that implement and assure security services in a

communication system, particularly those that provide data

confidentiality and data integrity and that authenticate

communicating entities.

management methods and processes, devices that implement them, and

the life cycle management of keying material and devices.

$ community string

(I) A community name in the form of an octet string that serves as

a cleartext password in SNMP version 1. [R1157]

$ compartment

(I) A grouping of sensitive information items that require special

access controls beyond those normally provided for the basic

classification level of the information. (See: category.)

procedures to be used for the information.

$ compromise

See: data compromise, security compromise.

$ compromised key list (CKL)

(O) MISSI usage: A list that identifies keys for which

unauthorized disclosure or alteration may have occurred. (See:

compromise.)

lists only KMIDs, not subjects that hold the keys, and not

certificates in which the keys are bound.

$ COMPUSEC

See: computer security.

$ computer emergency response team (CERT)

(I) An organization that studies computer and network INFOSEC in

order to provide incident response services to victims of attacks,

publish alerts concerning vulnerabilities and threats, and offer

other information to help improve computer and network security.

(See: CSIRT, security incident.)

University (sometimes called "the" CERT) and the Computer Incident

Advisory Capability.

$ Computer Incident Advisory Capability (CIAC)

(N) A computer emergency response team in the U.S. Department of

Energy.

$ computer network

(I) A collection of host computers together with the subnetwork or

internetwork through which they can exchange data.

types, ranging from the complex Internet to a simple system

composed of a personal computer dialing in as a remote terminal of

another computer.

$ computer security (COMPUSEC)

(I) Measures that implement and assure security services in a

computer system, particularly those that assure access control

service.

technical characteristics of computer hardware and software,

especially operating systems.

$ computer security incident response team (CSIRT)

(I) An organization "that coordinates and supports the response to

security incidents that involve sites within a defined

constituency." [R2350] (See: CERT, FIRST, security incident.)

- Provide a (secure) channel for receiving reports about

suspected security incidents.

- Provide assistance to members of its constituency in handling

the incidents.

- Disseminate incident-related information to its constituency

and other involved parties.

$ computer security object

(I) The definition or representation of a resource, tool, or

mechanism used to maintain a condition of security in computerized

environments. Includes many elements referred to in standards that

are either selected or defined by separate user communities.

[CSOR] (See: object identifier, Computer Security Objects

$ Computer Security Objects Register (CSOR)

(N) A service operated by NIST is establishing a catalog for

computer security objects to provide stable object definitions

identified by unique names. The use of this register will enable

the unambiguous specification of security parameters and

algorithms to be used in secure data exchanges.

international standards community and ANSI. Those guidelines

establish minimum responsibilities for registration authorities

and assign the top branches of an international registration

hierarchy. Under that international registration hierarchy the

CSOR is responsible for the allocation of unique identifiers under

the branch {joint-iso-ccitt(2) country(16) us(840) gov(101)

csor(3)}.

$ COMSEC

See: communication security.

$ confidentiality

See: data confidentiality.

$ configuration control

(I) The process of regulating changes to hardware, firmware,

software, and documentation throughout the development and

operational life of a system. (See: administrative security.)

malicious alteration of a system and thus provides assurance of

system integrity. (See: malicious logic.)

$ confinement property

See: (secondary definition under) Bell-LaPadula Model.

$ connectionless data integrity service

(I) A security service that provides data integrity service for an

individual IP datagram, by detecting modification of the datagram,

without regard to the ordering of the datagram in a stream of

datagrams.

detect lost or reordered datagrams within a stream of datagrams.

$ contingency plan

(I) A plan for emergency response, backup operations, and post-

disaster recovery in a system as part of a security program to

ensure availability of critical system resources and facilitate

continuity of operations in a crisis. [NCS04] (See: availability.)

$ controlled security mode

(D) ISDs SHOULD NOT use this term. It was defined in an earlier

version of the U.S. Department of Defense policy that regulates

system accreditation, but was subsumed by "partitioned security

mode" in the current version. [DOD2]

system, wherein at least some users with access to the system have

neither a security clearance nor a need-to-know for all classified

material contained in the system. However, separation and control

of users and classified material on the basis, respectively, of

clearance and classification level are not essentially under

operating system control like they are in "multilevel security

mode".

the security requirements of Defense policy in ways less

restrictive than "dedicated security mode" and "system high

security mode", but at a level of risk lower than that generally

associated with the true "multilevel security mode". This was to

be accomplished by implementation of explicit augmenting measures

to reduce or remove a substantial measure of system software

vulnerability together with specific limitation of the security

clearance levels of users permitted concurrent access to the

system.

$ cookie

(I) access control usage: A synonym for "capability" or "ticket"

in an access control system.

(I) IPsec usage: Data exchanged by ISAKMP to prevent certain

denial-of-service attacks during the establishment of a security

association.

(I) HTTP usage: Data exchanged between an HTTP server and a

browser (a client of the server) to store state information on the

client side and retrieve it later for server use.

a cookie, which the client retains after the HTTP connection

closes. A server can use this mechanism to maintain persistent

client-side state information for HTTP-based applications,

retrieving the state information in later connections. A cookie

may include a description of the range of URLs for which the state

is valid. Future requests made by the client in that range will

also send the current value of the cookie to the server. Cookies

can be used to generate profiles of web usage habits, and thus may

infringe on personal privacy.

$ Coordinated Universal Time (UTC)

(N) UTC is derived from International Atomic Time (TAI) by adding

a number of leap seconds. The International Bureau of Weights and

Measures computes TAI once each month by averaging data from many

laboratories. (See: GeneralizedTime, UTCTime.)

$ copy

See: card copy.

$ correctness integrity

(I) Accuracy and consistency of the information that data values

represent, rather than of the data itself. Closely related to

issues of accountability and error handling. (See: data integrity,

source integrity.)

$ correctness proof

(I) A mathematical proof of consistency between a specification

for system security and the implementation of that specification.

(See: formal specification.)

$ countermeasure

(I) An action, device, procedure, or technique that reduces a

threat, a vulnerability, or an attack by eliminating or preventing

it, by minimizing the harm it can cause, or by discovering and

reporting it so that corrective action can be taken.

a protocol feature, an element function, or a usage constraint.

$ country code

(I) An identifier that is defined for a nation by ISO. [I3166]

character alphabetic code, a unique three-character alphabetic

code, and a three-digit code. Among many uses of these codes, the

two-character codes are used as top-level domain names.

$ covert channel

(I) A intra-system channel that permits two cooperating entities,

without exceeding their access authorizations, to transfer

information in a way that violates the system's security policy.

(See: channel, out of band.)

(O) "A communications channel that allows two cooperating

processes to transfer information in a manner that violates the

system's security policy." [NCS04]

insider and an outsider. Of course, an outsider has no access

authorization at all. A covert channel is a system feature that

the system architects neither designed nor intended for

information transfer:

- "Timing channel": A system feature that enable one system

entity to signal information to another by modulating its own

use of a system resource in such a way as to affect system

response time observed by the second entity.

- "Storage channel": A system feature that enables one system

entity to signal information to another entity by directly or

indirectly writing a storage location that is later directly or

indirectly read by the second entity.

$ CPS

See: certification practice statement.

$ cracker

(I) Someone who tries to break the security of, and gain access

to, someone else's system without being invited to do so. (See:

hacker and intruder.)

$ CRAM

See: Challenge-Response Authentication Mechanism.

$ CRC

See: cyclic redundancy check.

$ credential(s)

(I) Data that is transferred or presented to establish either a

claimed identity or the authorizations of a system entity. (See:

authentication information, capability, ticket.)

(O) "Data that is transferred to establish the claimed identity of

an entity." [I7498 Part 2]

$ critical

1. (I) "Critical" system resource: A condition of a service or

other system resource such that denial of access to (i.e., lack of

availability of) that resource would jeopardize a system user's

ability to perform a primary function or would result in other

serious consequences. (See: availability, sensitive.)

2. (N) "Critical" extension: Each extension of an X.509

certificate (or CRL) is marked as being either critical or non-

critical. If an extension is critical and a certificate user (or

CRL user) does not recognize the extension type or does not

implement its semantics, then the user is required to treat the

certificate (or CRL) as invalid. If an extension is non-critical,

a user that does not recognize or implement that extension type is

permitted to ignore the extension and process the rest of the

certificate (or CRL).

$ CRL

See: certificate revocation list.

$ CRL distribution point

See: distribution point.

$ CRL extension

See: extension.

$ cross-certificate

See: cross-certification.

$ cross-certification

(I) The act or process by which two CAs each certify a public key

of the other, issuing a public-key certificate to that other CA.

certificate when the users are certified under different

certification hierarchies.

$ cryptanalysis

(I) The mathematical science that deals with analysis of a

cryptographic system in order to gain knowledge needed to break or

circumvent the protection that the system is designed to provide.

(See: cryptology.)

(O) "The analysis of a cryptographic system and/or its inputs and

outputs to derive confidential variables and/or sensitive data

including cleartext." [I7498 Part 2]

cryptanalysis--convert the ciphertext to plaintext (which usually

is cleartext) without knowing the key--but that definition applies

only to encryption systems. Today, the term is used with reference

to all kinds of cryptographic algorithms and key management, and

the "I" definition reflects that. In all cases, however, a

cryptanalyst tries to uncover or reproduce someone else's

sensitive data, such as cleartext, a key, or an algorithm. The

basic cryptanalytic attacks on encryption systems are ciphertext-

only, known-plaintext, chosen-plaintext, and chosen-ciphertext;

and these generalize to the other kinds of cryptography.

$ crypto

(D) Except as part of certain long-established terms listed in

this Glossary, ISDs SHOULD NOT use this abbreviated term because

it may be misunderstood. Instead, use "cryptography" or

"cryptographic".

$ cryptographic algorithm

(I) An algorithm that employs the science of cryptography,

including encryption algorithms, cryptographic hash algorithms,

digital signature algorithms, and key agreement algorithms.

$ cryptographic application programming interface (CAPI)

(I) The source code formats and procedures through which an

application program accesses cryptographic services, which are

defined abstractly compared to their actual implementation. For

example, see: PKCS #11, [R2628].

$ cryptographic card

(I) A cryptographic token in the form of a smart card or a PC

card.

$ cryptographic component

(I) A generic term for any system component that involves

cryptography. (See: cryptographic module.)

$ cryptographic hash

See: (secondary definition under) hash function.

$ cryptographic ignition key (CIK)

(I) A physical (usually electronic) token used to store,

transport, and protect cryptographic keys. (Sometimes abbreviated

as "crypto ignition key".)

cryptographic module, so that it is necessary to combine the two

to regenerate a key-encrypting key and thus activate the module

and other keys it contains.

$ cryptographic key

(I) Usually shortened to just "key". An input parameter that

varies the transformation performed by a cryptographic algorithm.

(O) "A sequence of symbols that controls the operations of

encipherment and decipherment." [I7498 Part 2]

symbols (usually bits) that comprise it should be random, or at

least pseudo-random, because that makes the key hard for an

adversary to guess. (See: cryptanalysis, brute force attack.)

$ Cryptographic Message Syntax (CMS)

(I) A encapsulation syntax for digital signatures, hashes, and

encryption of arbitrary messages. [R2630]

ASN.1 and use BER encoding. The syntax permits multiple

encapsulation with nesting, permits arbitrary attributes to be

signed along with message content, and supports a variety of

architectures for digital certificate-based key management.

$ cryptographic module

(I) A set of hardware, software, firmware, or some combination

thereof that implements cryptographic logic or processes,

including cryptographic algorithms, and is contained within the

module's cryptographic boundary, which is an explicitly defined

contiguous perimeter that establishes the physical bounds of the

module. [FP140]

$ cryptographic system

(I) A set of cryptographic algorithms together with the key

management processes that support use of the algorithms in some

application context.

the following "O" definition:

(O) "A collection of transformations from plaintext into

ciphertext and vice versa [which would exclude digital signature,

cryptographic hash, and key agreement algorithms], the particular

transformation(s) to be used being selected by keys. The

transformations are normally defined by a mathematical algorithm."

[X509]

$ cryptographic token

(I) A portable, user-controlled, physical device used to store

cryptographic information and possibly perform cryptographic

functions. (See: cryptographic card, token.)

algorithms and may implement related algorithms and key management

functions, such as a random number generator. A smart

cryptographic token may contain a cryptographic module or may not

be explicitly designed that way.

$ cryptography

(I) The mathematical science that deals with transforming data to

render its meaning unintelligible (i.e., to hide its semantic

content), prevent its undetected alteration, or prevent its

unauthorized use. If the transformation is reversible,

cryptography also deals with restoring encrypted data to

intelligible form. (See: cryptology, steganography.)

(O) "The discipline which embodies principles, means, and methods

for the transformation of data in order to hide its information

content, prevent its undetected modification and/or prevent its

unauthorized use. . . . Cryptography determines the methods used

in encipherment and decipherment." [I7498 Part 2]

$ Cryptoki

See: (secondary definition under) PKCS #11.

$ cryptology

(I) The science that includes both cryptography and cryptanalysis,

and sometimes is said to include steganography.

$ cryptonet

(I) A group of system entities that share a secret cryptographic

key for a symmetric algorithm.

$ cryptoperiod

(I) The time span during which a particular key is authorized to

be used in a cryptographic system. (See: key management.)

time, but sometimes is stated in terms of the maximum amount of

data permitted to be processed by a cryptographic algorithm using

the key. Specifying a cryptoperiod involves a tradeoff between the

cost of rekeying and the risk of successful cryptanalysis.

established in COMPUSEC usage. (See: crypto) In the context of

certificates and public keys, "key lifetime" and "validity period"

are often used instead.

$ cryptosystem

(D) ISDs SHOULD NOT use this term as an abbreviation for

cryptographic system. (For rationale, see: crypto.)

$ CSIRT

See: computer security incident response team.

$ CSOR

See: Computer Security Objects Register.

$ cut-and-paste attack

(I) An active attack on the data integrity of ciphertext, effected

by replacing sections of ciphertext with other ciphertext, such

that the result appears to decrypt correctly but actually decrypts

to plaintext that is forged to the satisfaction of the attacker.

$ cyclic redundancy check (CRC)

(I) Sometimes called "cyclic redundancy code". A type of checksum

algorithm that is not a cryptographic hash but is used to

implement data integrity service where accidental changes to data

are expected.

$ DAC

See: Data Authentication Code, discretionary access control.

$ DASS

See: Distributed Authentication Security Service.

$ data

(I) Information in a specific physical representation, usually a

sequence of symbols that have meaning; especially a representation

of information that can be processed or produced by a computer.

$ Data Authentication Algorithm

(N) A keyed hash function equivalent to DES cipher block chaining

with IV = 0. [A9009]

(D) ISDs SHOULD NOT use the uncapitalized form of this term as a

synonym for other kinds of checksums.

$ data authentication code vs. Data Authentication Code (DAC)

1. (N) Capitalized: "The Data Authentication Code" refers to a

U.S. Government standard [FP113] for a checksum that is computed

by the Data Authentication Algorithm. (Also known as the ANSI

standard Message Authentication Code [A9009].)

2. (D) Not capitalized: ISDs SHOULD NOT use "data authentication

code" as a synonym for another kind of checksum, because this term

mixes concepts in a potentially misleading way. (See:

authentication code.) Instead, use "checksum", "error detection

code", "hash", "keyed hash", "Message Authentication Code", or

"protected checksum", depending on what is meant.

$ data compromise

(I) A security incident in which information is exposed to

potential unauthorized access, such that unauthorized disclosure,

alteration, or use of the information may have occurred. (See:

compromise.)

$ data confidentiality

(I) "The property that information is not made available or

disclosed to unauthorized individuals, entities, or processes

[i.e., to any unauthorized system entity]." [I7498 Part 2]. (See:

data confidentiality service.)

(D) ISDs SHOULD NOT use this term as a synonym for "privacy",

which is a different concept.

$ data confidentiality service

(I) A security service that protects data against unauthorized

disclosure. (See: data confidentiality.)

(D) ISDs SHOULD NOT use this term as a synonym for "privacy",

which is a different concept.

$ Data Encryption Algorithm (DEA)

(N) A symmetric block cipher, defined as part of the U.S.

Government's Data Encryption Standard. DEA uses a 64-bit key, of

which 56 bits are independently chosen and 8 are parity bits, and

maps a 64-bit block into another 64-bit block. [FP046] (See: DES,

symmetric cryptography.)

has also been adopted in standards outside the Government (e.g.,

[A3092]).

$ data encryption key (DEK)

(I) A cryptographic key that is used to encipher application data.

(See: key-encrypting key.)

$ Data Encryption Standard (DES)

(N) A U.S. Government standard [FP046] that specifies the Data

Encryption Algorithm and states policy for using the algorithm to

protect unclassified, sensitive data. (See: AES, DEA.)

$ data integrity

(I) The property that data has not been changed, destroyed, or

lost in an unauthorized or accidental manner. (See: data integrity

service.)

(O) "The property that information has not been modified or

destroyed in an unauthorized manner." [I7498 Part 2]

with the information that the values represent (see: correctness

integrity) or the trustworthiness of the source of the values

(see: source integrity).

$ data integrity service

(I) A security service that protects against unauthorized changes

to data, including both intentional change or destruction and

accidental change or loss, by ensuring that changes to data are

detectable. (See: data integrity.)

it to an appropriate system entity; changes cannot be prevented

unless the system is perfect (error-free) and no malicious user

has access. However, a system that offers data integrity service

might also attempt to correct and recover from changes.

services: Although data integrity service is defined separately

from data origin authentication service and peer entity

authentication service, it is closely related to them.

Authentication services depend, by definition, on companion data

integrity services. Data origin authentication service provides

verification that the identity of the original source of a

received data unit is as claimed; there can be no such

verification if the data unit has been altered. Peer entity

authentication service provides verification that the identity of

a peer entity in a current association is as claimed; there can be

no such verification if the claimed identity has been altered.

$ data origin authentication

(I) "The corroboration that the source of data received is as

claimed." [I7498 Part 2] (See: authentication.)

$ data origin authentication service

(I) A security service that verifies the identity of a system

entity that is claimed to be the original source of received data.

(See: authentication, authentication service.)

holds the data. Unlike peer entity authentication service, this

service is independent of any association between the originator

and the recipient, and the data in question may have originated at

any time in the past.

service, because someone who does not know the private key cannot

forge the correct signature. However, by using the signer's public

key, anyone can verify the origin of correctly signed data.

integrity service. (See: (relationship between data integrity

service and authentication services under) data integrity service.

$ data privacy

(D) ISDs SHOULD NOT use this term because it mix concepts in a

potentially misleading way. Instead, use either "data

confidentiality" or "privacy", depending on what is meant.

$ data security

(I) The protection of data from disclosure, alteration,

destruction, or loss that either is accidental or is intentional

but unauthorized.

are needed to achieve data security.

$ datagram

(I) "A self-contained, independent entity of data carrying

sufficient information to be routed from the source to the

destination." [R1983]

$ DEA

See: Data Encryption Algorithm.

$ deception

See: (secondary definition under) threat consequence.

$ decipher

(D) ISDs SHOULD NOT use this term as a synonym for "decrypt",

except in special circumstances. (See: (usage discussion under)

encryption.)

$ decipherment

(D) ISDs SHOULD NOT use this term as a synonym for "decryption",

except in special circumstances. (See: (usage discussion under)

encryption.)

$ decode

(I) Convert encoded data back to its original form of

representation. (See: decrypt.)

(D) ISDs SHOULD NOT use this term as a synonym for "decrypt",

because that would mix concepts in a potentially misleading way.

$ decrypt

(I) Cryptographically restore ciphertext to the plaintext form it

had before encryption.

$ decryption

See: (secondary definition under) encryption.

$ dedicated security mode

(I) A mode of operation of an information system, wherein all

users have the clearance or authorization, and the need-to-know,

for all data handled by the system. In this mode, the system may

handle either a single classification level or category of

information or a range of levels and categories. [DOD2]

policy regarding system accreditation, but the term is also used

outside the Defense Department and outside the Government.

$ default account

(I) A system login account (usually accessed with a user name and

password) that has been predefined in a manufactured system to

permit initial access when the system is first put into service.

each copy of the system. In any case, when the system is put into

service, the default password should immediately be changed or the

default account should be disabled.

$ degauss

(N) Apply a magnetic field to permanently remove, erase, or clear

data from a magnetic storage medium, such as a tape or disk

[NCS25]. Reduce magnetic flux density to zero by applying a

reversing magnetic field.

$ degausser

(N) An electrical device that can degauss magnetic storage media.

$ DEK

See: data encryption key.

$ delta CRL

(I) A partial CRL that only contains entries for X.509

certificates that have been revoked since the issuance of a prior,

base CRL. This method can be used to partition CRLs that become

too large and unwieldy.

$ denial of service

(I) The prevention of authorized access to a system resource or

the delaying of system operations and functions. (See:

availability, critical (resource of a system), flooding.)

$ DES

See: Data Encryption Standard.

$ dictionary attack

(I) An attack that uses a brute-force technique of successively

trying all the words in some large, exhaustive list.

all possible passwords; or an attack on encryption by encrypting

some known plaintext phrase with all possible keys so that the key

for any given encrypted message containing that phrase may be

obtained by lookup.

$ Diffie-Hellman

(N) A key agreement algorithm published in 1976 by Whitfield

Diffie and Martin Hellman [DH76, R2631].

However, the key that it produces may be used for encryption, for

further key management operations, or for any other cryptography.

equal to the difficulty of computing discrete logarithms modulo a

large prime. The algorithm is described in [R2631] and [Schn]. In

brief, Alice and Bob together pick large integers that satisfy

certain mathematical conditions, and then use the integers to each

separately compute a public-private key pair. They send each other

their public key. Each person uses their own private key and the

other person's public key to compute a key, k, that, because of

the mathematics of the algorithm, is the same for each of them.

Passive wiretapping cannot learn the shared k, because k is not

transmitted, and neither are the private keys needed to compute k.

However, without additional mechanisms to authenticate each party

to the other, a protocol based on the algorithm may be vulnerable

to a man-in-the-middle attack.

$ digest

See: message digest.

$ digital certificate

(I) A certificate document in the form of a digital data object (a

data object used by a computer) to which is appended a computed

digital signature value that depends on the data object. (See:

attribute certificate, capability, public-key certificate.)

(D) ISDs SHOULD NOT use this term to refer to a signed CRL or CKL.

Although the recommended definition can be interpreted to include

those items, the security community does not use the term with

those meanings.

$ digital certification

(D) ISDs SHOULD NOT use this term as a synonym for

"certification", unless the context is not sufficient to

distinguish between digital certification and another kind of

certification, in which case it would be better to use "public-key

certification" or another phrase that indicates what is being

certified.

$ digital document

(I) An electronic data object that represents information

originally written in a non-electronic, non-magnetic medium

(usually ink on paper) or is an analogue of a document of that

type.

$ digital envelope

(I) A digital envelope for a recipient is a combination of (a)

encrypted content data (of any kind) and (b) the content

encryption key in an encrypted form that has been prepared for the

use of the recipient.

because, although the term is defined in PKCS #7 and used in

S/MIME, it is not yet widely established.

data confidentiality with encryption; digital enveloping is a

hybrid encryption scheme to "seal" a message or other data, by

encrypting the data and sending both it and a protected form of

the key to the intended recipient, so that no one other than the

intended recipient can "open" the message. In PCKS #7, it means

first encrypting the data using a symmetric encryption algorithm

and a secret key, and then encrypting the secret key using an

asymmetric encryption algorithm and the public key of the intended

recipient. In S/MIME, additional methods are defined for

conveying the content encryption key.

$ Digital ID(service mark)

(D) ISDs SHOULD NOT use this term as a synonym for "digital

certificate" because (a) it is the service mark of a commercial

firm, (b) it unnecessarily duplicates the meaning of other, well-

established terms, and (c) a certificate is not always used as

authentication information. In some contexts, however, it may be

useful to explain that the key conveyed in a public-key

certificate can be used to verify an identity and, therefore, that

the certificate can be thought of as digital identification

information. (See: identification information.)

$ digital key

"cryptographic key", unless the context is insufficient to

distinguish the digital key from another kind of key, such as a

metal key for a door lock.

$ digital notary

(I) Analogous to a notary public. Provides a trusted date-and-time

stamp for a document, so that someone can later prove that the

document existed at a point in time. May also verify the

signature(s) on a signed document before applying the stamp. (See:

notarization.)

$ digital signature

(I) A value computed with a cryptographic algorithm and appended

to a data object in such a way that any recipient of the data can

use the signature to verify the data's origin and integrity. (See:

data origin authentication service, data integrity service,

digitized signature, electronic signature, signer.)

(I) "Data appended to, or a cryptographic transformation of, a

data unit that allows a recipient of the data unit to prove the

source and integrity of the data unit and protect against forgery,

e.g. by the recipient." [I7498 Part 2]

and then the hash result is cryptographically transformed using a

private key of the signer. The final resulting value is called the

digital signature of the data object. The signature value is a

protected checksum, because the properties of a cryptographic hash

ensure that if the data object is changed, the digital signature

will no longer match it. The digital signature is unforgeable

because one cannot be certain of correctly creating or changing

the signature without knowing the private key of the supposed

signer.

algorithm (e.g., see: RSA) to transform the hash result. Thus,

when Alice needs to sign a message to send to Bob, she can use her

private key to encrypt the hash result. Bob receives both the

message and the digital signature. Bob can use Alice's public key

to decrypt the signature, and then compare the plaintext result to

the hash result that he computes by hashing the message himself.

If the values are equal, Bob accepts the message because he is

certain that it is from Alice and has arrived unchanged. If the

values are not equal, Bob rejects the message because either the

message or the signature was altered in transit.

hash result with an algorithm (e.g., see: DSA, El Gamal) that

cannot be directly used to encrypt data. Such a scheme creates a

signature value from the hash and provides a way to verify the

signature value, but does not provide a way to recover the hash

result from the signature value. In some countries, such a scheme

may improve exportability and avoid other legal constraints on

usage.

$ Digital Signature Algorithm (DSA)

(N) An asymmetric cryptographic algorithm that produces a digital

signature in the form of a pair of large numbers. The signature is

computed using rules and parameters such that the identity of the

signer and the integrity of the signed data can be verified. (See:

Digital Signature Standard.)

$ Digital Signature Standard (DSS)

(N) The U.S. Government standard [FP186] that specifies the

Digital Signature Algorithm (DSA), which involves asymmetric

cryptography.

$ digital watermarking

(I) Computing techniques for inseparably embedding unobtrusive

marks or labels as bits in digital data--text, graphics, images,

video, or audio--and for detecting or extracting the marks later.

hidden, usually imperceptible, and always intended to be

unobtrusive. Depending on the particular technique that is used,

digital watermarking can assist in proving ownership, controlling

duplication, tracing distribution, ensuring data integrity, and

performing other functions to protect intellectual property

rights. [ACM]

$ digitized signature

(D) ISDs SHOULD NOT use this term because there is no current

consensus on its definition. Although it appears to be used mainly

to refer to various forms of digitized images of handwritten

signatures, the term should be avoided because it might be

confused with "digital signature".

$ directory

$ Directory

See: directory vs. Directory.

$ Directory Access Protocol (DAP)

(N) An OSI protocol [X519] for communication between a Directory

User Agent (a client) and a Directory System Agent (a server).

(See: Lightweight Directory Access Protocol.)

$ directory vs. Directory

1. (I) Not capitalized: The term "directory" refers generically to

a database server or other system that provides information--such

as a digital certificate or CRL--about an entity whose name is

known.

2. (I) Capitalized: "Directory" refers specifically to the X.500

Directory. (See: repository.)

$ disaster plan

(D) A synonym for "contingency plan". In the interest of

consistency, ISDs SHOULD use "contingency plan" instead of

"disaster plan".

$ disclosure (i.e., unauthorized disclosure)

See: (secondary definition under) threat consequence.

$ discretionary access control (DAC)

(I) An access control service that enforces a security policy

based on the identity of system entities and their authorizations

to access system resources. (See: access control list, identity-

based security policy, mandatory access control.)

have access rights that permit the entity, by its own volition, to

enable another entity to access some resource.

(O) "A means of restricting access to objects based on the

identity of subjects and/or groups to which they belong. The

controls are discretionary in the sense that a subject with a

certain access permission is capable of passing that permission

(perhaps indirectly) on to any other subject." [DOD1]

$ disruption

See: (secondary definition under) threat consequence.

$ Distinguished Encoding Rules (DER)

(N) A subset of the Basic Encoding Rules, which gives exactly one

way to represent any ASN.1 value as an octet string [X690].

is used in applications in which a unique encoding is needed, such

as when a digital signature is computed on an ASN.1 value.

$ distinguished name (DN)

(I) An identifier that uniquely represents an object in the X.500

Directory Information Tree (DIT) [X501]. (See: domain name.)

leading from the base of the DIT to the object that is named. An

X.509 public-key certificate or CRL contains a DN that identifies

its issuer, and an X.509 attribute certificate contains a DN or

other form of name that identifies its subject.

$ Distributed Authentication Security Service (DASS)

(I) An experimental Internet protocol [R1507] that uses

cryptographic mechanisms to provide strong, mutual authentication

services in a distributed environment.

$ distribution point

(I) An X.500 Directory entry or other information source that is

named in a v3 X.509 public-key certificate extension as a location

from which to obtain a CRL that might list the certificate.

"cRLDistributionPoints" extension that names places to get CRLs on

which the certificate might be listed. A CRL obtained from a

distribution point may (a) cover either all reasons for which a

certificate might be revoked or only some of the reasons, (b) be

issued by either the authority that signed the certificate or some

other authority, and (c) contain revocation entries for only a

subset of the full set of certificates issued by one CA or (c')

contain revocation entries for multiple CAs.

$ DN

See: distinguished name.

$ DNS

See: Domain Name System.

$ DOI

See: Domain of Interpretation.

$ domain

(I) Security usage: An environment or context that is defined by a

security policy, security model, or security architecture to

include a set of system resources and the set of system entities

that have the right to access the resources. (See: domain of

interpretation, security perimeter.)

(I) Internet usage: That part of the Internet domain name space

tree [R1034] that is at or below the name the specifies the

domain. A domain is a subdomain of another domain if it is

contained within that domain. For example, D.C.B.A is a subdomain

of C.B.A. (See: Domain Name System.)

(O) MISSI usage: The domain of a MISSI CA is the set of MISSI

users whose certificates are signed by the CA.

(O) OSI usage: An administrative partition of a complex

distributed OSI system.

$ domain name

(I) The style of identifier--a sequence of case-insensitive ASCII

labels separated by dots ("bbn.com.")--defined for subtrees in the

Internet Domain Name System [R1034] and used in other Internet

identifiers, such as host names (e.g., "rosslyn.bbn.com."),

mailbox names (e.g., "rshirey@bbn.com."), and URLs (e.g.,

"http://www.rosslyn.bbn.com/foo"). (See: distinguished name,

domain.)

each node and leaf holds records describing a resource. Each node

has a label. The domain name of a node is the list of labels on

the path from the node to the root of the tree. The labels in a

domain name are printed or read left to right, from the most

specific (lowest, farthest from the root) to the least specific

(highest, closest to the root). The root's label is the null

string, so a complete domain name properly ends in a dot. The top-

level domains, those immediately below the root, include COM, EDU,

GOV, INT, MIL, NET, ORG, and two-letter country codes (such as US)

from ISO-3166. [R1591] (See: country code.)

$ Domain Name System (DNS)

(I) The main Internet operations database, which is distributed

over a collection of servers and used by client software for

purposes such as translating a domain name-style host name into an

IP address (e.g., "rosslyn.bbn.com" is "192.1.7.10") and locating

a host that accepts mail for some mailbox address. [R1034]

- Domain name space and resource records: Specifications for the

tree-structured domain name space, and data associated with the

names.

- Name servers: Programs that hold information about a subset of

the tree's structure and data holdings, and also hold pointers

to other name servers that can provide information from any

part of the tree.

- Resolvers: Programs that extract information from name servers

in response to client requests; typically, system routines

directly accessible to user programs.

distribution for public keys needed for the DNS and for other

protocols, (b) data origin authentication service and data

integrity service for resource records, (c) data origin

authentication service for transactions between resolvers and

servers, and (d) access control of records.

$ domain of interpretation (DOI)

(I) IPsec usage: An ISAKMP/IKE DOI defines payload formats,

exchange types, and conventions for naming security-relevant

information such as security policies or cryptographic algorithms

and modes.

the TSIG's CIPSO Working Group.

$ dominate

(I) Security level A is said to "dominate" security level B if the

hierarchical classification level of A is greater (higher) than or

equal to that of B and the nonhierarchical categories of A include

all of those of B.

$ dongle

(I) A portable, physical, electronic device that is required to be

attached to a computer to enable a particular software program to

run. (See: token.)

protection of software, because the program will not run unless

the matching dongle is attached. When the software runs, it

periodically queries the dongle and quits if the dongle does not

reply with the proper authentication information. Dongles were

originally constructed as an EPROM (erasable programmable read-

only memory) to be connected to a serial input-output port of a

personal computer.

$ downgrade

(I) Reduce the classification level of information in an

authorized manner.

$ draft RFC

(D) ISDs SHOULD NOT use this term, because the Request for Comment

series is archival in nature and does not have a "draft" category.

(Instead, see: Internet Draft, Draft Standard (in Internet

Standard).)

$ DSA

See: Digital Signature Algorithm.

$ DSS

See: Digital Signature Standard.

$ dual control

(I) A procedure that uses two or more entities (usually persons)

operating in concert to protect a system resource, such that no

single entity acting alone can access that resource. (See: no-lone

zone, separation of duties, split knowledge.)

$ dual signature

(D) ISDs SHOULD NOT use this term except when stated as

"SET(trademark) dual signature" with the following meaning:

(O) SET usage: A single digital signature that protects two

separate messages by including the hash results for both sets in a

single encrypted value. [SET2]

the two hash results, and then hashing that value and encrypting

the result with the signer's private key. Done to reduce the

number of encryption operations and to enable verification of data

integrity without complete disclosure of the data.

$ EAP

See: Extensible Authentication Protocol

$ eavesdropping

(I) Passive wiretapping done secretly, i.e., without the knowledge

of the originator or the intended recipients of the communication.

$ ECB

See: electronic codebook.

$ ECDSA

See: Elliptic Curve Digital Signature Algorithm.

$ economy of mechanism

(I) The principle that each security mechanism should be designed

to be as simple as possible, so that the mechanism can be

correctly implemented and so that it can be verified that the

operation of the mechanism enforces the containing system's

security policy. (See: least privilege.)

$ EDI

See: electronic data interchange.

$ EDIFACT

See: (secondary definition under) electronic data interchange.

$ EE

(D) ISDs SHOULD NOT use this abbreviation because of possible

confusion among "end entity", "end-to-end encryption", "escrowed

encryption standard", and other terms.

$ EES

See: Escrowed Encryption Standard.

$ El Gamal algorithm

(N) An algorithm for asymmetric cryptography, invented in 1985 by

Taher El Gamal, that is based on the difficulty of calculating

discrete logarithms and can be used for both encryption and

digital signatures. [ElGa, Schn]

$ electronic codebook (ECB)

(I) An block cipher mode in which a plaintext block is used

directly as input to the encryption algorithm and the resultant

output block is used directly as ciphertext [FP081].

$ electronic commerce

(I) General usage: Business conducted through paperless exchanges

of information, using electronic data interchange, electronic

funds transfer (EFT), electronic mail, computer bulletin boards,

facsimile, and other paperless technologies.

(O) SET usage: "The exchange of goods and services for payment

between the cardholder and merchant when some or all of the

transaction is performed via electronic communication." [SET2]

$ electronic data interchange (EDI)

(I) Computer-to-computer exchange, between trading partners, of

business data in standardized document formats.

by EDIFACT (EDI for Administration, Commerce, and Transportation),

which is an international, UN-sponsored standard primarily used in

Europe and Asia. X12 and EDIFACT are aligning to create a single,

global EDI standard.

$ electronic signature

(D) ISDs SHOULD NOT use this term because there is no current

consensus on its definition. (Instead, see: digital signature.)

$ elliptic curve cryptography (ECC)

(I) A type of asymmetric cryptography based on mathematics of

groups that are defined by the points on a curve.

stronger per bit of key (against cryptanalysis that uses a brute

force attack) than any other known form of asymmetric

cryptography. ECC is based on mathematics different than the kinds

originally used to define the Diffie-Hellman algorithm and the

Digital Signature Algorithm. ECC is based on the mathematics of

groups defined by the points on a curve, where the curve is

defined by a quadratic equation in a finite field. ECC can be used

to define both an algorithm for key agreement that is an analog of

Diffie-Hellman and an algorithm for digital signature that is an

analog of DSA. (See: ECDSA.)

$ Elliptic Curve Digital Signature Algorithm (ECDSA)

(N) A standard [A9062] that is the elliptic curve cryptography

analog of the Digital Signature Algorithm.

$ emanation

(I) An signal (electromagnetic, acoustic, or other medium) that is

emitted by a system (through radiation or conductance) as a

consequence (i.e., byproduct) of its operation, and that may

contain information. (See: TEMPEST.)

$ emanations security (EMSEC)

(I) Physical constraints to prevent information compromise through

signals emanated by a system, particular the application of

TEMPEST technology to block electromagnetic radiation.

$ emergency plan

(D) A synonym for "contingency plan". In the interest of

consistency, ISDs SHOULD use "contingency plan" instead of

"emergency plan".

$ EMSEC

See: emanations security.

$ EMV

(I) An abbreviation of "Europay, MasterCard, Visa". Refers to a

specification for smart cards that are used as payment cards, and

for related terminals and applications. [EMV1, EMV2, EMV3]

$ Encapsulating Security Payload (ESP)

(I) An Internet IPsec protocol [R2406] designed to provide a mix

of security services--especially data confidentiality service--in

the Internet Protocol. (See: Authentication Header.)

protocol, or in a nested fashion with tunneling. Security services

can be provided between a pair of communicating hosts, between a

pair of communicating security gateways, or between a host and a

gateway. The ESP header is encapsulated by the IP header, and the

ESP header encapsulates either the upper layer protocol header

(transport mode) or an IP header (tunnel mode). ESP can provide

data confidentiality service, data origin authentication service,

connectionless data integrity service, an anti-replay service, and

limited traffic flow confidentiality. The set of services depends

on the placement of the implementation and on options selected

when the security association is established.

$ encipher

(D) ISDs SHOULD NOT use this term as a synonym for "encrypt".

However, see the usage note under "encryption".

$ encipherment

(D) ISDs SHOULD NOT use this term as a synonym for "encryption",

except in special circumstances that are explained in the usage

discussion under "encryption".

$ encode

(I) Use a system of symbols to represent information, which might

originally have some other representation. (See: decode.)

(D) ISDs SHOULD NOT use this term as a synonym for "encrypt",

because encoding is not usually intended to conceal meaning.

$ encrypt

(I) Cryptographically transform data to produce ciphertext. (See:

encryption.)

$ encryption

(I) Cryptographic transformation of data (called "plaintext") into

a form (called "ciphertext") that conceals the data's original

meaning to prevent it from being known or used. If the

transformation is reversible, the corresponding reversal process

is called "decryption", which is a transformation that restores

encrypted data to its original state. (See: cryptography.)

encrypt" (and related variations: encryption, decrypt, and

decryption). However, because of cultural biases, some

international usage, particularly ISO and CCITT standards, avoids

"to encrypt" and instead uses the verb "to encipher" (and related

variations: encipherment, decipher, decipherment).

(O) "The cryptographic transformation of data (see: cryptography)

to produce ciphertext." [I7498 Part 2]

cleartext. But in some cases, the plaintext may be ciphertext that

was output from another encryption operation. (See:

superencryption.)

transforming data. In addition to the data to be transformed, the

algorithm has one or more inputs that are control parameters: (a)

a key value that varies the transformation and, in some cases, (b)

an initialization value that establishes the starting state of the

algorithm.

$ encryption certificate

(I) A public-key certificate that contains a public key that is

intended to be used for encrypting data, rather than for verifying

digital signatures or performing other cryptographic functions.

C) A v3 X.509 public-key certificate may have a "keyUsage"

extension that indicates the purpose for which the certified

public key is intended.

$ end entity

(I) A system entity that is the subject of a public-key

certificate and that is using, or is permitted and able to use,

the matching private key only for a purpose or purposes other than

signing a digital certificate; i.e., an entity that is not a CA.

(D) "A certificate subject which uses its public [sic] key for

purposes other than signing certificates." [X509]

misleading and incomplete. First, the X.509 definition should say

"private key" rather than "public key" because certificates are

not usefully signed with a public key. Second, the X.509

definition is weak regarding whether an end entity may or may not

use the private key to sign a certificate, i.e., whether the

subject may be a CA. The intent of X.509's authors was that an end

entity certificate is not valid for use in verifying a signature

on an X.509 certificate or X.509 CRL. Thus, it would have been

better for the X.509 definition to have said "only for purposes

other than signing certificates".

is useful in describing applications of asymmetric cryptography.

The way the term is used in X.509 implies that it was meant to be

defined, as we have done here, relative to roles that an entity

(which is associated with an OSI end system) is playing or is

permitted to play in applications of asymmetric cryptography other

than the PKI that supports applications.

either the same or different certificates, is a matter of policy.

(See: certification practice statement.) A v3 X.509 public-key

certificate may have a "basicConstraints" extension containing a

"cA" value that specifically "indicates whether or not the public

key may be used to verify certificate signatures".

$ end system

(I) An OSI term for a computer that implements all seven layers of

the OSIRM and may attach to a subnetwork. (In the context of the

Internet Protocol Suite, usually called a "host".)

$ end-to-end encryption

(I) Continuous protection of data that flows between two points in

a network, provided by encrypting data when it leaves its source,

leaving it encrypted while it passes through any intermediate

computers (such as routers), and decrypting only when the data

arrives at the intended destination. (See: link encryption,

wiretapping.)

that are connected by one or more intermediate relays, end-to-end

encryption enables the source and destination systems to protect

their communications without depending on the intermediate systems

to provide the protection.

$ end user

(I) General usage: A system entity, usually a human individual,

that makes use of system resources, primarily for application

purposes as opposed to system management purposes.

(I) PKI usage: A synonym for "end entity"; but the term "end

entity" is preferred.

$ entity

See: system entity.

$ entrapment

(I) "The deliberate planting of apparent flaws in a system for the

purpose of detecting attempted penetrations or confusing an

intruder about which flaws to exploit." [FP039] (See: honey pot.)

$ ephemeral key

(I) A public key or a private key that is relatively short-lived.

(See: session key.)

$ error detection code

(I) A checksum designed to detect, but not correct, accidental

(i.e., unintentional) changes in data.

$ Escrowed Encryption Standard (EES)

(N) A U.S. Government standard [FP185] that specifies use of a

symmetric encryption algorithm (SKIPJACK) and a Law Enforcement

Access Field (LEAF) creation method to implement part of a key

escrow system that provides for decryption of encrypted

telecommunications when interception is lawfully authorized.

used to encrypt and decrypt unclassified, sensitive

telecommunications data.

$ ESP

See: Encapsulating Security Payload.

$ Estelle

(N) A language (ISO 9074-1989) for formal specification of

computer network protocols.

$ evaluated products list

(O) General usage: A list of information system equipment items

that have been evaluated against, and found to be compliant with,

a particular set of criteria.

(O) U.S. Department of Defense usage: The Evaluated Products List

(http://www.radium.ncsc.mil/tpep/epl/) contains items that have

been evaluated against the TCSEC by the NCSC, or against the

Common Criteria by the NCSC or one of its partner agencies in

another county. The List forms Chapter 4 of NSA's "Information

Systems Security Products and Services Catalogue".

$ evaluated system

(I) Refers to a system that has been evaluated against security

criteria such as the TCSEC or the Common Criteria.

$ expire

See: certificate expiration.

$ exposure

See: (secondary definition under) threat consequence.

$ Extensible Authentication Protocol

(I) A framework that supports multiple, optional authentication

mechanisms for PPP, including cleartext passwords, challenge-

response, and arbitrary dialog sequences. [R2284]

router that connects to a PPP network server via switched circuits

or dial-up lines.

$ extension

(I) A data item defined for optional inclusion in a v3 X.509

public-key certificate or a v2 X.509 CRL.

methods for associating additional attributes with subjects and

public keys and for managing a certification hierarchy:

- "Certificate extension": X.509 defines standard extensions that

may be included in v3 certificates to provide additional key

and security policy information, subject and issuer attributes,

and certification path constraints.

- "CRL extension": X.509 defines extensions that may be included

in v2 CRLs to provide additional issuer key and name

information, revocation reasons and constraints, and

information about distribution points and delta CRLs.

- "Private extension": Additional extensions, each named by an

OID, can be locally defined as needed by applications or

communities. (See: PKIX private extension, SET private

extensions.)

$ extranet

(I) A computer network that an organization uses to carry

application data traffic between the organization and its business

partners. (See: intranet.)

Internet or using Internet technology, by constructing the

extranet as a VPN.

$ fail safe

(I) A mode of system termination that automatically leaves system

processes and components in a secure state when a failure occurs

or is detected in the system.

$ fail soft

(I) Selective termination of affected non-essential system

functions and processes when a failure occurs or is detected in

the system.

$ failure control

(I) A methodology used to provide fail-safe or fail-soft

termination and recovery of functions and processes when failures

are detected or occur in a system. [FP039]

$ Federal Information Processing Standards (FIPS)

(N) The Federal Information Processing Standards Publication (FIPS

PUB) series issued by the U.S. National Institute of Standards and

Technology as technical guidelines for U.S. Government

procurements of information processing system equipment and

services. [FP031, FP039, FP046, FP081, FP102, FP113, FP140, FP151,

FP180, FP185, FP186, FP188]

Property and Administrative Services Act of 1949 as amended by the

Computer Security Act of 1987, Public Law 100-235.

$ Federal Public-key Infrastructure (FPKI)

(N) A PKI being planned to establish facilities, specifications,

and policies needed by the U.S. Federal Government to use public-

key certificates for INFOSEC, COMSEC, and electronic commerce

involving unclassified but sensitive applications and interactions

between Federal agencies as well as with entities of other

branches of the Federal Government, state, and local governments,

business, and the public. [FPKI]

$ Federal Standard 1027

(N) An U.S. Government document defining emanation, anti-tamper,

security fault analysis, and manual key management criteria for

DES encryption devices, primary for OSI layer 2. Was renamed "FIPS

PUB 140" when responsibility for protecting unclassified,

sensitive information was transferred from NSA to NIST, and then

was superseded by FIPS PUB 140-1.

$ File Transfer Protocol (FTP)

(I) A TCP-based, application-layer, Internet Standard protocol

[R0959] for moving data files from one computer to another.

$ filtering router

(I) An internetwork router that selectively prevents the passage

of data packets according to a security policy.

firewall. A router usually receives a packet from a network and

decides where to forward it on a second network. A filtering

router does the same, but first decides whether the packet should

be forwarded at all, according to some security policy. The policy

is implemented by rules (packet filters) loaded into the router.

The rules mostly involve values of data packet control fields

(especially IP source and destination addresses and TCP port

numbers). [R2179]

$ financial institution

(N) "An establishment responsible for facilitating customer-

initiated transactions or transmission of funds for the extension

of credit or the custody, loan, exchange, or issuance of money."

[SET2]

$ fingerprint

(I) A pattern of curves formed by the ridges on a fingertip. (See:

biometric authentication, thumbprint.)

(D) ISDs SHOULD NOT use this term as a synonym for "hash result"

because it mixes concepts in a potentially misleading way.

(D) ISDs SHOULD NOT use this term with the following PGP

definition, because the term and definition mix concepts in a

potentially misleading way and duplicate the meaning of "hash

result":

(O) PGP usage: A hash result used to authenticate a public key

(key fingerprint) or other data. [PGP]

$ FIPS

See: Federal Information Processing Standards.

$ FIPS PUB 140-1

(N) The U.S. Government standard [FP140] for security requirements

to be met by a cryptographic module used to protect unclassified

information in computer and communication systems. (See: Common

Criteria, FIPS, Federal Standard 1027.)

to "Level 4") of requirements to cover a wide range of potential

applications and environments. The requirements address basic

design and documentation, module interfaces, authorized roles and

services, physical security, software security, operating system

security, key management, cryptographic algorithms,

electromagnetic interference and electromagnetic compatibility

(EMI/EMC), and self-testing. NIST and the Canadian Communication

Security Establishment jointly certify modules.

$ firewall

(I) An internetwork gateway that restricts data communication

traffic to and from one of the connected networks (the one said to

be "inside" the firewall) and thus protects that network's system

resources against threats from the other network (the one that is

said to be "outside" the firewall). (See: guard, security

gateway.)

as a corporate LAN, or even just one host) from a larger network

(such as the Internet). The firewall is installed at the point

where the networks connect, and the firewall applies security

policy rules to control traffic that flows in and out of the

protected network.

firewall may consist of a pair of filtering routers and one or

more proxy servers running on one or more bastion hosts, all

connected to a small, dedicated LAN between the two routers. The

external router blocks attacks that use IP to break security (IP

address spoofing, source routing, packet fragments), while proxy

servers block attacks that would exploit a vulnerability in a

higher layer protocol or service. The internal router blocks

traffic from leaving the protected network except through the

proxy servers. The difficult part is defining criteria by which

packets are denied passage through the firewall, because a

firewall not only needs to keep intruders out, but usually also

needs to let authorized users in and out.

$ firmware

(I) Computer programs and data stored in hardware--typically in

read-only memory (ROM) or programmable read-only memory (PROM)--

such that the programs and data cannot be dynamically written or

modified during execution of the programs. (See: hardware,

software.)

$ FIRST

See: Forum of Incident Response and Security Teams.

$ flaw hypothesis methodology

(I) An evaluation or attack technique in which specifications and

documentation for a system are analyzed to hypothesize flaws in

the system. The list of hypothetical flaws is prioritized on the

basis of the estimated probability that a flaw exists and,

assuming it does, on the ease of exploiting it and the extent of

control or compromise it would provide. The prioritized list is

used to direct a penetration test or attack against the system.

[NCS04]

$ flooding

(I) An attack that attempts to cause a failure in (especially, in

the security of) a computer system or other data processing entity

by providing more input than the entity can process properly.

(See: denial of service.)

$ flow analysis

(I) An analysis performed on a nonprocedural formal system

specification that locates potential flows of information between

system variables. By assigning security levels to the variables,

the analysis can find some types of covert channels.

$ flow control

(I) A procedure or technique to ensure that information transfers

within a system are not made from one security level to another

security level, and especially not from a higher level to a lower

level. (See: covert channel, simple security property, confinement

property.)

$ formal specification

(I) A specification of hardware or software functionality in a

computer-readable language; usually a precise mathematical

description of the behavior of the system with the aim of

providing a correctness proof.

$ formulary

(I) A technique for enabling a decision to grant or deny access to

be made dynamically at the time the access is attempted, rather

than earlier when an access control list or ticket is created.

$ FORTEZZA(trademark)

(N) A registered trademark of NSA, used for a family of

interoperable security products that implement a NIST/NSA-approved

suite of cryptographic algorithms for digital signature, hash,

encryption, and key exchange. The products include a PC card that

contains a CAPSTONE chip, serial port modems, server boards, smart

cards, and software implementations.

$ Forum of Incident Response and Security Teams (FIRST)

(N) An international consortium of CSIRTs that work together to

handle computer security incidents and promote preventive

activities. (See: CSIRT, security incident.)

nearly 70 members spanning the globe. Its mission includes:

- Provide members with technical information, tools, methods,

assistance, and guidance.

- Coordinate proactive liaison activities and analytical support.

- Encourage development of quality products and services.

- Improve national and international information security for

government, private industry, academia, and the individual.

- Enhance the image and status of the CSIRT community.

$ forward secrecy

See: public-key forward secrecy.

$ FPKI

See: Federal Public-Key Infrastructure.

$ FTP

See: File Transfer Protocol.

$ gateway

(I) A relay mechanism that attaches to two (or more) computer

networks that have similar functions but dissimilar

implementations and that enables host computers on one network to

communicate with hosts on the other; an intermediate system that

is the interface between two computer networks. (See: bridge,

firewall, guard, internetwork, proxy server, router, and

subnetwork.)

practice, they operate at OSI layer 3 (see: bridge, router) or

layer 7 (see: proxy server). When the two networks differ in the

protocol by which they offer service to hosts, the gateway may

translate one protocol into another or otherwise facilitate

interoperation of hosts (see: Internet Protocol).

$ GCA

See: geopolitical certificate authority.

$ GeneralizedTime

(N) The ASN.1 data type "GeneralizedTime" (specified in ISO 8601)

contains a calendar date (YYYYMMDD) and a time of day, which is

either (a) the local time, (b) the Coordinated Universal Time, or

Universal Time to be calculated. (See: Coordinated Universal Time,

UTCTime.)

$ Generic Security Service Application Program Interface (GSS-API)

(I) An Internet Standard protocol [R2078] that specifies calling

conventions by which an application (typically another

communication protocol) can obtain authentication, integrity, and

confidentiality security services independently of the underlying

security mechanisms and technologies, thus allowing the

application source code to be ported to different environments.

GSS-API implementation and transfers the tokens to a peer on a

remote system; that peer passes the received tokens to its local

GSS-API implementation for processing. The security services

available through GSS-API in this fashion are implementable (and

have been implemented) over a range of underlying mechanisms based

on [symmetric] and [asymmetric cryptography]." [R2078]

$ geopolitical certificate authority (GCA)

(O) SET usage: In a SET certification hierarchy, an optional level

that is certified by a BCA and that may certify cardholder CAs,

merchant CAs, and payment gateway CAs. Using GCAs enables a brand

to distribute responsibility for managing certificates to

geographic or political regions, so that brand policies can vary

between regions as needed.

$ Green Book

(D) Except as an explanatory appositive, ISDs SHOULD NOT use this

term as a synonym for "Defense Password Management Guideline"

[CSC2]. Instead, use the full proper name of the document or, in

subsequent references, a conventional abbreviation. (See: Rainbow

Series.)

(D) Usage note: To improve international comprehensibility of

Internet Standards and the Internet Standards Process, ISDs SHOULD

NOT use "cute" synonyms for document titles. No matter how popular

and clearly understood a nickname may be in one community, it is

likely to cause confusion in others. For example, several other

information system standards also are called "the Green Book". The

following are some examples:

- Each volume of 1992 ITU-T (at that time, CCITT) standards.

- "PostScript Language Program Design", Adobe Systems, Addison-

Wesley, 1988.

- IEEE 1003.1 POSIX Operating Systems Interface.

- "Smalltalk-80: Bits of History, Words of Advice", Glenn

Krasner, Addison-Wesley, 1983.

- "X/Open Compatibility Guide".

- A particular CD-ROM format developed by Phillips.

$ GRIP

(I) A contraction of "Guidelines and Recommendations for Security

Incident Processing", the name of the IETF working group that

seeks to facilitate consistent handling of security incidents in

the Internet community. (See: security incident.)

vendors, network service providers, and response teams in their

roles assisting organizations in resolving security incidents.

These relationships are functional and can exist within and across

organizational boundaries.

$ GSS-API

See: Generic Security Service Application Program Interface.

$ guard

(I) A gateway that is interposed between two networks (or

computers, or other information systems) operating at different

security levels (one level is usually higher than the other) and

is trusted to mediate all information transfers between the two

levels, either to ensure that no sensitive information from the

first (higher) level is disclosed to the second (lower) level, or

to protect the integrity of data on the first (higher) level.

(See: firewall.)

$ guest login

See: anonymous login.

$ GULS

(I) Generic Upper Layer Security service element (ISO 11586), a

five-part standard for the exchange of security information and

security-transformation functions that protect confidentiality and

integrity of application data.

$ hacker

(I) Someone with a strong interest in computers, who enjoys

learning about them and experimenting with them. (See: cracker.)

(circa 1960), which then had a neutral or positive connotation of

"someone who figures things out and makes something cool

happen". Today, the term is frequently misused, especially by

journalists, to have the pejorative meaning of cracker.

$ handle

(I) (1.) Verb: Perform processing operations on data, such as

receive and transmit, collect and disseminate, create and delete,

store and retrieve, read and write, and compare. (2.) Noun: An on-

line pseudonym, particularly one used by a cracker; derived from

citizens band radio culture.

$ hardware

(I) The material physical components of a computer system. (See:

firmware, software.)

$ hardware token

See: token.

$ hash code

(D) ISDs SHOULD NOT use this term (especially not as a synonym for

"hash result") because it mixes concepts in a potentially

misleading way. A hash result is not a "code" in any sense defined

by this glossary. (See: code, hash result, hash value, message

digest.)

$ hash function

(I) An algorithm that computes a value based on a data object

(such as a message or file; usually variable-length; possibly very

large), thereby mapping the data object to a smaller data object

(the "hash result") which is usually a fixed-size value. (See:

checksum, keyed hash.)

(O) "A (mathematical) function which maps values from a large

(possibly very large) domain into a smaller range. A 'good' hash

function is such that the results of applying the function to a

(large) set of values in the domain will be evenly distributed

(and apparently at random) over the range." [X509]

called a "cryptographic hash function", an algorithm for which it

is computationally infeasible (because no attack is significantly

more efficient than brute force) to find either (a) a data object

that maps to a pre-specified hash result (the "one-way" property)

or (b) two data objects that map to the same hash result (the

"collision-free" property). (See: MD2, MD4, MD5, SHA-1.)

definition for hash function. Any change to an input data object

will, with high probability, result in a different hash result, so

that the result of a cryptographic hash makes a good checksum for

a data object.

$ hash result

(I) The output of a hash function. (See: hash code, hash value.)

(O) "The output produced by a hash function upon processing a

message" (where "message" is broadly defined as "a digital

representation of data"). [ABA] (The recommended definition is

compatible with this ABA definition, but we avoid the unusual

definition of "message".)

$ hash value

(D) ISDs SHOULD NOT use this term (especially not as a synonym for

"hash result", the output of a hash function) because it might be

confused with "hashed value" (the input to a hash function). (See:

hash code, hash result, message digest.)

$ hierarchical PKI

(I) A PKI architecture based on a certification hierarchy. (See:

mesh PKI, trust-file PKI.)

$ hierarchy management

(I) The process of generating configuration data and issuing

public-key certificates to build and operate a certification

hierarchy.

$ hierarchy of trust

(D) ISDs SHOULD NOT use this term with regard to PKI, especially

not as a synonym for "certification hierarchy", because this term

mixes concepts in a potentially misleading way. (See:

certification hierarchy, trust, web of trust.)

$ hijack attack

(I) A form of active wiretapping in which the attacker seizes

control of a previously established communication association.

(See: man-in-the-middle attack, pagejacking, piggyback attack.)

$ HMAC

(I) A keyed hash [R2104] that can be based on any iterated

cryptographic hash (e.g., MD5 or SHA-1), so that the cryptographic

strength of HMAC depends on the properties of the selected

cryptographic hash. (See: [R2202, R2403, R2404].)

function is iterated on data blocks of length B bytes. L is the

length of the of hash result of H. K is a secret key of length L

<= K <= B. The values IPAD and OPAD are fixed strings used as

inner and outer padding and defined as follows: IPAD = the byte

0x36 repeated B times, OPAD = the byte 0x5C repeated B times. HMAC

is computed by H(K XOR OPAD, H(K XOR IPAD, inputdata)).

- To use available cryptographic hash functions without

modification, particularly functions that perform well in

software and for which software is freely and widely available.

- To preserve the original performance of the selected hash

without significant degradation.

- To use and handle keys in a simple way.

- To have a well-understood cryptographic analysis of the

strength of the mechanism based on reasonable assumptions about

the underlying hash function.

- To enable easy replacement of the hash function in case a

faster or stronger hash is found or required.

$ honey pot

(I) A system (e.g., a web server) or a system resource (e.g., a

file on a server), that is designed to be attractive to potential

crackers and intruders, like honey is attractive to bears. (See:

entrapment.)

(D) It is likely that other cultures have different metaphors for

this concept. To ensure international understanding, ISDs should

not use this term unless they also provide an explanation like

this one. (See: (usage note under) Green Book.)

$ host

(I) General computer network usage: A computer that is attached to

a communication subnetwork or internetwork and can use services

provided by the network to exchange data with other attached

systems. (See: end system.)

(I) Specific Internet Protocol Suite usage: A networked computer

that does not forward Internet Protocol packets that are not

addressed to the computer itself. (See: router.)

guests, providing application layer services or access to other

computers attached to the network. However, even though some

traditional peripheral service devices, such as printers, can now

be independently connected to networks, they are not usually

called hosts.

$ Html

See: Hypertext Markup Language.

$ HTTP

See: Hypertext Transfer Protocol.

$ https

(I) When used in the first part of a URL (the part that precedes

the colon and specifies an access scheme or protocol), this term

specifies the use of HTTP enhanced by a security mechanism, which

is usually SSL. (See: S-HTTP.)

$ hybrid encryption

(I) An application of cryptography that combines two or more

encryption algorithms, particularly a combination of symmetric and

asymmetric encryption. (E.g., see: digital envelope.)

equivalently strong symmetric ones. Thus, asymmetric encryption is

not normally used for data confidentiality except in distributing

symmetric keys in applications where the key data is usually short

(in terms of bits) compared to the data it protects. (E.g., see:

MSP, PEM, PGP.)

$ hyperlink

(I) In hypertext or hypermedia, an information object (such as a

word, a phrase, or an image; usually highlighted by color or

underscoring) that points (indicates how to connect) to related

information that is located elsewhere and can be retrieved by

activating the link (e.g., by selecting the object with a mouse

pointer and then clicking).

$ hypermedia

(I) A generalization of hypertext; any media that contain

hyperlinks that point to material in the same or another data

object.

$ hypertext

(I) A computer document, or part of a document, that contains

hyperlinks to other documents; i.e., text that contains active

pointers to other text. Usually written in Hypertext Markup

Language and accessed using a web browser. (See: hypermedia.)

$ Hypertext Markup Language (HTML)

(I) A platform-independent system of syntax and semantics for

adding characters to data files (particularly text files) to

represent the data's structure and to point to related data, thus

creating hypertext for use in the World Wide Web and other

applications. [R1866]

$ Hypertext Transfer Protocol (HTTP)

(I) A TCP-based, application-layer, client-server, Internet

protocol [R2616] used to carry data requests and responses in the

World Wide Web. (See: hypertext.)

$ IAB

See: Internet Architecture Board.

$ IANA

See: Internet Assigned Numbers Authority.

$ ICANN

See: Internet Corporation for Assigned Names and Numbers.

$ ICMP

See: Internet Control Message Protocol.

$ ICMP flood

(I) A denial of service attack that sends a host more ICMP echo

request ("ping") packets than the protocol implementation can

handle. (See: flooding, smurf.)

$ ICRL

See: indirect certificate revocation list.

$ IDEA

See: International Data Encryption Algorithm.

$ identification

(I) An act or process that presents an identifier to a system so

that the system can recognize a system entity and distinguish it

from other entities. (See: authentication.)

$ Identification Protocol

(I) An client-server Internet protocol [R1413] for learning the

identity of a user of a particular TCP connection.

string that identifies the owner of that connection on the

server's system. The protocol is not intended for authorization or

access control. At best, it provides additional auditing

information with respect to TCP.

$ identity-based security policy

(I) "A security policy based on the identities and/or attributes

of users, a group of users, or entities acting on behalf of the

users and the resources/objects being accessed." [I7498 Part 2]

(See: rule-based security policy.)

$ IEEE

See: Institute of Electrical and Electronics Engineers, Inc.

$ IEEE 802.10

(N) An IEEE committee developing security standards for local area

networks. (See: SILS.)

$ IEEE P1363

(N) An IEEE working group, Standard for Public-Key Cryptography,

developing a comprehensive reference standard for asymmetric

cryptography. Covers discrete logarithm (e.g., DSA), elliptic

curve, and integer factorization (e.g., RSA); and covers key

agreement, digital signature, and encryption.

$ IESG

See: Internet Engineering Steering Group.

$ IETF

See: Internet Engineering Task Force.

$ IKE

See: IPsec Key Exchange.

$ IMAP4

See: Internet Message Access Protocol, version 4.

$ IMAP4 AUTHENTICATE

(I) A IMAP4 "command" (better described as a transaction type, or

a protocol-within-a-protocol) by which an IMAP4 client optionally

proposes a mechanism to an IMAP4 server to authenticate the client

to the server and provide other security services. (See: POP3.)

performing a challenge-response authentication protocol and,

optionally, negotiating a protection mechanism for subsequent POP3

interactions. The security mechanisms that are used by IMAP4

AUTHENTICATE--including Kerberos, GSSAPI, and S/Key--are described

in [R1731].

$ in the clear

(I) Not encrypted. (See: cleartext.)

$ indirect certificate revocation list (ICRL)

(I) In X.509, a CRL that may contain certificate revocation

notifications for certificates issued by CAs other than the issuer

of the ICRL.

$ indistinguishability

(I) An attribute of an encryption algorithm that is a

formalization of the notion that the encryption of some string is

indistinguishable from the encryption of an equal-length string of

nonsense.

"semantic security".

$ information

(I) Facts and ideas, which can be represented (encoded) as various

forms of data.

$ Information Technology Security Evaluation Criteria (ITSEC)

(N) Standard developed for use in the European Union; accommodates

a wider range of security assurance and functionality combinations

than the TCSEC. Superseded by the Common Criteria. [ITSEC]

$ INFOSEC

(I) Abbreviation for "information security", referring to security

measures that implement and assure security services in computer

systems (i.e., COMPUSEC) and communication systems (i.e., COMSEC).

$ initialization value (IV)

(I) An input parameter that sets the starting state of a

cryptographic algorithm or mode. (Sometimes called "initialization

vector" or "message indicator".)

addition to that provided by a key (see: salt), and to synchronize

one cryptographic process with another. For an example of the

latter, cipher block chaining mode requires an IV. [R2405]

$ initialization vector

(D) For consistency, ISDs SHOULD NOT use this term as a synonym

for "initialization value".

$ insider attack

See: (secondary definition under) attack.

$ Institute of Electrical and Electronics Engineers, Inc. (IEEE)

(N) The IEEE is a not-for-profit association of more than 330,000

individual members in 150 countries. The IEEE produces 30 percent

of the world's published literature in electrical engineering,

computers, and control technology; holds annually more than 300

major conferences; and has more than 800 active standards with 700

under development. (See: Standards for Interoperable LAN/MAN

Security.)

$ integrity

See: data integrity, correctness integrity, source integrity,

system integrity.

$ integrity check

(D) ISDs SHOULD NOT use this term as a synonym for "cryptographic

hash" or "protected checksum", because this term unnecessarily

duplicates the meaning of other, well-established terms.

$ intelligent threat

(I) A circumstance in which an adversary has the technical and

operational capability to detect and exploit a vulnerability and

also has the demonstrated, presumed, or inferred intent to do so.

(See: threat.)

$ International Data Encryption Algorithm (IDEA)

(N) A patented, symmetric block cipher that uses a 128-bit key and

operates on 64-bit blocks. [Schn] (See: symmetric cryptography.)

$ International Standard

See: (secondary definition under) ISO.

$ International Traffic in Arms Regulations (ITAR)

(N) Rules issued by the U.S. State Department, by authority of the

Arms Export Control Act (22 U.S.C. 2778), to control export and

import of defense articles and defense services, including

information security systems, such as cryptographic systems, and

TEMPEST suppression technology. (See: Wassenaar Arrangement.)

$ internet

$ Internet

See: internet vs. Internet.

$ Internet Architecture Board (IAB)

(I) A technical advisory group of the ISOC, chartered by the ISOC

Trustees to provide oversight of Internet architecture and

protocols and, in the context of Internet Standards, a body to

which decisions of the IESG may be appealed. Responsible for

approving appointments to the IESG from among nominees submitted

by the IETF nominating committee. [R2026]

$ Internet Assigned Numbers Authority (IANA)

(I) From the early days of the Internet, the IANA was chartered by

the ISOC and the U.S. Government's Federal Network Council to be

the central coordination, allocation, and registration body for

parameters for Internet protocols. Superseded by ICANN.

$ Internet Control Message Protocol (ICMP)

(I) An Internet Standard protocol [R0792] that is used to report

error conditions during IP datagram processing and to exchange

other information concerning the state of the IP network.

$ Internet Corporation for Assigned Names and Numbers (ICANN)

(I) The non-profit, private corporation that has assumed

responsibility for the IP address space allocation, protocol

parameter assignment, domain name system management, and root

server system management functions formerly performed under U.S.

Government contract by IANA and other entities.

IESG, contains numerous parameters, such as internet addresses,

domain names, autonomous system numbers, protocol numbers, port

numbers, management information base object identifiers, including

private enterprise numbers, and many others. The Internet

community requires that the values used in these parameter fields

be assigned uniquely. ICANN makes those assignments as requested

and maintains a registry of the current values.

Internet's business, technical, and academic communities. The U.S.

Government designated ICANN to serve as the global consensus

entity with responsibility for coordinating four key functions for

the Internet: the allocation of IP address space, the assignment

of protocol parameters, the management of the DNS, and the

management of the DNS root server system.

$ Internet Draft

(I) A working document of the IETF, its areas, and its working

groups. (Other groups may also distribute working documents as

Internet Drafts.) An Internet Draft is not an archival document

like an RFCis. Instead, an Internet Draft is a preliminary or

working document that is valid for a maximum of six months and may

be updated, replaced, or made obsolete by other documents at any

time. It is inappropriate to use an Internet Draft as reference

material or to cite it other than as "work in progress."

$ Internet Engineering Steering Group (IESG)

(I) The part of the ISOC responsible for technical management of

IETF activities and administration of the Internet Standards

Process according to procedures approved by the ISOC Trustees.

Directly responsible for actions along the "standards track",

including final approval of specifications as Internet Standards.

Composed of IETF Area Directors and the IETF chairperson, who also

chairs the IESG. [R2026]

$ Internet Engineering Task Force (IETF)

(I) A self-organized group of people who make contributions to the

development of Internet technology. The principal body engaged in

developing Internet Standards, although not itself a part of the

ISOC. Composed of Working Groups, which are arranged into Areas

(such as the Security Area), each coordinated by one or more Area

Directors. Nominations to the IAB and the IESG are made by a

committee selected at random from regular IETF meeting attendees

who have volunteered. [R2026, R2323]

$ Internet Message Access Protocol, version 4 (IMAP4)

(I) An Internet protocol [R2060] by which a client workstation can

dynamically access a mailbox on a server host to manipulate and

retrieve mail messages that the server has received and is holding

for the client. (See: POP3.)

a server and providing other security services. (See: IMAP4

AUTHENTICATE.)

$ Internet Policy Registration Authority (IPRA)

(I) An X.509-compliant CA that is the top CA of the Internet

certification hierarchy operated under the auspices of the ISOC

[R1422]. (See: (PEM usage under) certification hierarchy.)

$ Internet Protocol (IP)

(I) A Internet Standard protocol (version 4 [R0791] and version 6

[R2460]) that moves datagrams (discrete sets of bits) from one

computer to another across an internetwork but does not provide

reliable delivery, flow control, sequencing, or other end-to-end

services that TCP provides. (See: IP address, TCP/IP.)

$ Internet Protocol security (IPsec)

(I) (1.) The name of the IETF working group that is specifying a

security architecture [R2401] and protocols to provide security

services for Internet Protocol traffic. (2.) A collective name for

that architecture and set of protocols. (Implementation of IPsec

protocols is optional for IP version 4, but mandatory for IP

version 6.) (See: Internet Protocol Security Option.)

and ESP), (b) security associations (what they are, how they work,

how they are managed, and associated processing), (c) key

management (IKE), and (d) algorithms for authentication and

encryption. The set of security services include access control

service, connectionless data integrity service, data origin

authentication service, protection against replays (detection of

the arrival of duplicate datagrams, within a constrained window),

data confidentiality service, and limited traffic flow

confidentiality.

$ Internet Protocol Security Option (IPSO)

(I) Refers to one of three types of IP security options, which are

fields that may be added to an IP datagram for the purpose of

carrying security information about the datagram. (See: IPsec.)

(D) ISDs SHOULD NOT use this term without a modifier to indicate

which of the three types is meant.

1. "DoD Basic Security Option" (IP option type 130): Defined for

use on U.S. Department of Defense common user data networks.

Identifies the Defense classification level at which the

datagram is to be protected and the protection authorities

whose rules apply to the datagram. [R1108]

A "protection authority" is a National Access Program (e.g.,

GENSER, SIOP-ESI, SCI, NSA, Department of Energy) or Special

Access Program that specifies protection rules for transmission

and processing of the information contained in the datagram.

[R1108]

2. "DoD Extended Security Option" (IP option type 133): Permits

additional security labeling information, beyond that present

in the Basic Security Option, to be supplied in the datagram to

meet the needs of registered authorities. [R1108]

3. "Common IP Security Option" (CIPSO) (IP option type 134):

security labels. (Formerly called "Commercial IP Security

Option".) Was published as Internet-Draft [CIPSO]; not advanced

to RFC.

$ Internet Protocol Suite

See: (secondary definition under) Internet.

$ Internet Security Association and Key Management Protocol (ISAKMP)

(I) An Internet IPsec protocol [R2408] to negotiate, establish,

modify, and delete security associations, and to exchange key

generation and authentication data, independent of the details of

any specific key generation technique, key establishment protocol,

encryption algorithm, or authentication mechanism.

protocols at all TCP/IP layers. By centralizing management of

security associations, ISAKMP reduces duplicated functionality

within each protocol. ISAKMP can also reduce connection setup

time, by negotiating a whole stack of services at once. Strong

authentication is required on ISAKMP exchanges, and a digital

signature algorithm based on asymmetric cryptography is used

within ISAKMP's authentication component.

$ Internet Society (ISOC)

(I) A professional society concerned with Internet development

(including technical Internet Standards); with how the Internet is

and can be used; and with social, political, and technical issues

that result. The ISOC Board of Trustees approves appointments to

the IAB from among nominees submitted by the IETF nominating

committee. [R2026]

$ Internet Standard

(I) A specification, approved by the IESG and published as an RFC,

that is stable and well-understood, is technically competent, has

multiple, independent, and interoperable implementations with

substantial operational experience, enjoys significant public

support, and is recognizably useful in some or all parts of the

Internet. [R2026] (See: RFC.)

is organized and managed by the IAB and the IESG. The process is

concerned with all protocols, procedures, and conventions used in

or by the Internet, whether or not they are part of the Internet

Protocol Suite. The "Internet Standards Track" has three levels of

increasing maturity: Proposed Standard, Draft Standard, and

Standard. (See: (standards levels under) ISO.)

$ Internet Standards document (ISD)

or other item that is produced as part of the Internet Standards

Process [R2026]. However, neither the term nor the abbreviation is

widely accepted and, therefore, SHOULD NOT be used in an ISD

unless it is accompanied by an explanation like this. (See:

Internet Standard.)

$ internet vs. Internet

1. (I) Not capitalized: A popular abbreviation for "internetwork".

2. (I) Capitalized: "The Internet" is the single, interconnected,

worldwide system of commercial, government, educational, and other

computer networks that share the set of protocols specified by the

IAB [R2026] and the name and address spaces managed by the ICANN.

also is popularly known as "TCP/IP", because TCP and IP are two of

its fundamental components. These protocols enable a user of any

one of the networks in the Internet to communicate with, or use

services located on, any of the other networks.

[R1958], no Internet Standard formally defines a layered reference

model for the IPS that is similar to the OSIRM. However, Internet

community documents do refer (inconsistently) to layers:

application, socket, transport, internetwork, network, data link,

and physical. In this Glossary, Internet layers are referred to by

name to avoid confusing them with OSIRM layers, which are referred

to by number.

$ internetwork

(I) A system of interconnected networks; a network of networks.

Usually shortened to "internet". (See: internet vs. Internet.)

connect a set of subnetworks. When the subnetworks differ in the

OSI layer 3 protocol service they provide, the gateways sometimes

implement a uniform internetwork protocol (e.g., IP) that operates

at the top of layer 3 and hides the underlying heterogeneity from

hosts that use communication services provided by the internet.

(See: router.)

$ intranet

(I) A computer network, especially one based on Internet

technology, that an organization uses for its own internal, and

usually private, purposes and that is closed to outsiders. (See:

extranet, virtual private network.)

$ intruder

(I) An entity that gains or attempts to gain access to a system or

system resource without having authorization to do so. (See:

cracker.)

$ intrusion

See: security intrusion.

$ intrusion detection

(I) A security service that monitors and analyzes system events

for the purpose of finding, and providing real-time or near real-

time warning of, attempts to access system resources in an

unauthorized manner.

$ invalidity date

(N) An X.509 CRL entry extension that "indicates the date at which

it is known or suspected that the [revoked certificate's private

key] was compromised or that the certificate should otherwise be

considered invalid" [X509].

entry, and may even be earlier than the date of issue of earlier

CRLs. However, the invalidity date is not, by itself, sufficient

for purposes of non-repudiation service. For example, to

fraudulently repudiate a validly-generated signature, a private

key holder may falsely claim that the key was compromised at some

time in the past.

$ IP

See: Internet Protocol.

$ IP address

(I) A computer's internetwork address that is assigned for use by

the Internet Protocol and other protocols.

8-bit numbers separated by periods. For example, the address of

the host named "rosslyn.bbn.com" is 192.1.7.10.

where each "x" is the hexadecimal value of one of the eight 16-bit

parts of the address. For example, 1080:0:0:0:8:800:200C:417A and

FEDC:BA98:7654:3210:FEDC:BA98:7654:3210.

$ IP Security Option

See: Internet Protocol Security Option.

$ IPRA

See: Internet Policy Registration Authority.

$ IPsec

See: Internet Protocol security.

$ IPsec Key Exchange (IKE)

(I) An Internet, IPsec, key-establishment protocol [R2409] (partly

based on OAKLEY) that is intended for putting in place

authenticated keying material for use with ISAKMP and for other

security associations, such as in AH and ESP.

$ IPSO

See: Internet Protocol Security Option.

$ ISAKMP

See: Internet Security Association and Key Management Protocol.

$ ISD

See: Internet Standards document.

$ ISO

(I) International Organization for Standardization, a voluntary,

non-treaty, non-government organization, established in 1947, with

voting members that are designated standards bodies of

participating nations and non-voting observer organizations. (See:

ANSI, ITU-T.)

and the IEC (the International Electrotechnical Commission) form

the specialized system for worldwide standardization. National

bodies that are members of ISO or IEC participate in developing

international standards through ISO and IEC technical committees

that deal with particular fields of activity. Other international

governmental and non-governmental organizations, in liaison with

ISO and IEC, also take part. (ANSI is the U.S. voting member of

ISO. ISO is a class D member of ITU-T.)

increasing maturity: Working Draft (WD), Committee Draft (CD),

Draft International Standard (DIS), and International Standard

(IS). (See: (standards track levels under) Internet Standard.) In

information technology, ISO and IEC have a joint technical

committee, ISO/IEC JTC 1. DISs adopted by JTC 1 are circulated to

national bodies for voting, and publication as an IS requires

approval by at least 75% of the national bodies casting a vote.

$ ISOC

See: Internet Society.

$ issue (a digital certificate or CRL)

(I) Generate and sign a digital certificate (or CRL) and, usually,

distribute it and make it available to potential certificate users

(or CRL users). (See: certificate creation.)

certificate creation, and exclude the act of publishing. In

general usage, however, "issuing" a digital certificate (or CRL)

includes not only certificate creation but also making it

available to potential users, such as by storing it in a

repository or other directory or otherwise publishing it.

$ issuer

1. (I) "Issuer" of a certificate or CRL: The CA that signs the

digital certificate or CRL.

name may include a common name value.

2. (N) "Issuer" of a payment card: SET usage: "The financial

institution or its agent that issues the unique primary account

number to the cardholder for the payment card brand." [SET2]

and issues the payment card also guarantees payment for authorized

transactions that use the card in accordance with card brand

regulations and local legislation. [SET1]

$ ITAR

See: International Traffic in Arms Regulations.

$ ITSEC

See: Information Technology System Evaluation Criteria.

$ ITU-T

(N) International Telecommunications Union, Telecommunication

Standardization Sector (formerly "CCITT"), a United Nations treaty

organization that is composed mainly of postal, telephone, and

telegraph authorities of the member countries and that publishes

standards called "Recommendations". (See: X.400, X.500.)

works on many kinds of communication systems. ITU-T cooperates

with ISO on communication protocol standards, and many

Recommendations in that area are also published as an ISO standard

with an ISO name and number.

$ IV

See: initialization value.

$ KDC

See: Key Distribution Center.

$ KEA

See: Key Exchange Algorithm.

$ KEK

See: key-encrypting key.

$ Kerberos

(N) A system developed at the Massachusetts Institute of

Technology that depends on passwords and symmetric cryptography

(DES) to implement ticket-based, peer entity authentication

service and access control service distributed in a client-server

network environment. [R1510, Stei]

three-headed dog guarding Hades.

$ key

See: cryptographic key.

$ key agreement (algorithm or protocol)

(I) A key establishment method (especially one involving

asymmetric cryptography) by which two or more entities, without

prior arrangement except a public exchange of data (such as public

keys), each computes the same key value. I.e., each can

independently generate the same key value, but that key cannot be

computed by other entities. (See: Diffie-Hellman, key

establishment, Key Exchange Algorithm, key transport.)

(O) "A method for negotiating a key value on line without

transferring the key, even in an encrypted form, e.g., the Diffie-

Hellman technique." [X509]

(O) "The procedure whereby two different parties generate shared

symmetric keys such that any of the shared symmetric keys is a

function of the information contributed by all legitimate

participants, so that no party [alone] can predetermine the value

of the key." [A9042]

can each use their own private key and the other's public key with

the Diffie-Hellman algorithm to first compute a shared secret

value and, from that value, derive a session key to encrypt the

message.

$ key authentication

(N) "The assurance of the legitimate participants in a key

agreement that no non-legitimate party possesses the shared

symmetric key." [A9042]

$ key center

(I) A centralized key distribution process (used in symmetric

cryptography), usually a separate computer system, that uses key-

encrypting keys (master keys) to encrypt and distribute session

keys needed in a community of users.

distribution center and key translation center.

$ key confirmation

(N) "The assurance of the legitimate participants in a key

establishment protocol that the intended parties sharing the

symmetric key actually possess the shared symmetric key." [A9042]

$ key distribution

(I) A process that delivers a cryptographic key from the location

where it is generated to the locations where it is used in a

cryptographic algorithm. (See: key management.)

$ key distribution center (KDC)

(I) A type of key center (used in symmetric cryptography) that

implements a key distribution protocol to provide keys (usually,

session keys) to two (or more) entities that wish to communicate

securely. (See: key translation center.)

communicate with each other but do not currently share keys, (b)

each share a KEK with the KDC, and (c) may not be able to generate

or acquire keys by themselves. Alice requests the keys from the

KDC. The KDC generates or acquires the keys and makes two

identical sets. The KDC encrypts one set in the KEK it shares with

Alice, and sends that encrypted set to Alice. The KDC encrypts the

second set in the KEK it shares with Bob, and either sends that

encrypted set to Alice for her to forward to Bob, or sends it

directly to Bob (although the latter option is not supported in

the ANSI standard [A9017]).

$ key encapsulation

See: (secondary definition under) key recovery.

$ key-encrypting key (KEK)

(I) A cryptographic key that is used to encrypt other keys, either

DEKs or other KEKs, but usually is not used to encrypt application

data.

$ key escrow

See: (secondary definition under) key recovery.

$ key establishment (algorithm or protocol)

(I) A process that combines the key generation and key

distribution steps needed to set up or install a secure

communication association. (See: key agreement, key transport.)

(O) "The procedure to share a symmetric key among different

parties by either key agreement or key transport." [A9042]

transport:

- Key transport: One entity generates a secret key and securely

sends it to the other entity. (Or each entity generates a

secret value and securely sends it to the other entity, where

the two values are combined to form a secret key.)

- Key agreement: No secret is sent from one entity to another.

Instead, both entities, without prior arrangement except a

public exchange of data, compute the same secret value. I.e.,

each can independently generate the same value, but that value

cannot be computed by other entities.

$ Key Exchange Algorithm (KEA)

(N) A key agreement algorithm [NIST] that is similar to the

Diffie-Hellman algorithm, uses 1024-bit asymmetric keys, and was

developed and formerly classified at the "Secret" level by NSA.

(See: CAPSTONE, CLIPPER, FORTEZZA, SKIPJACK.)

declassified.

$ key generation

(I) A process that creates the sequence of symbols that comprise a

cryptographic key. (See: key management.)

$ key generator

1. (I) An algorithm that uses mathematical rules to

deterministically produce a pseudo-random sequence of

cryptographic key values.

2. (I) An encryption device that incorporates a key generation

mechanism and applies the key to plaintext (e.g., by exclusive OR-

ing the key bit string with the plaintext bit string) to produce

ciphertext.

$ key length

(I) The number of symbols (usually bits) needed to be able to

represent any of the possible values of a cryptographic key. (See:

key space.)

$ key lifetime

(N) MISSI usage: An attribute of a MISSI key pair that specifies a

time span that bounds the validity period of any MISSI X.509

public-key certificate that contains the public component of the

pair. (See: cryptoperiod.)

$ key management

(I) The process of handling and controlling cryptographic keys and

related material (such as initialization values) during their life

cycle in a cryptographic system, including ordering, generating,

distributing, storing, loading, escrowing, archiving, auditing,

and destroying the material. (See: key distribution, key escrow,

keying material, public-key infrastructure.)

(O) "The generation, storage, distribution, deletion, archiving

and application of keys in accordance with a security policy."

[I7498 Part 2]

(O) "The activities involving the handling of cryptographic keys

and other related security parameters (e.g., IVs, counters) during

the entire life cycle of the keys, including their generation,

storage, distribution, entry and use, deletion or destruction, and

archiving." [FP140]

$ Key Management Protocol (KMP)

(N) A protocol to establish a shared symmetric key between a pair

(or a group) of users. (One version of KMP was developed by SDNS,

and another by SILS.)

$ key material identifier (KMID)

(N) MISSI usage: A 64-bit identifier that is assigned to a key

pair when the public key is bound in a MISSI X.509 public-key

certificate.

$ key pair

(I) A set of mathematically related keys--a public key and a

private key--that are used for asymmetric cryptography and are

generated in a way that makes it computationally infeasible to

derive the private key from knowledge of the public key (e.g.,

see: Diffie-Hellman, Rivest-Shamir-Adleman).

entities so they can use the key to encrypt data, verify a digital

signature, compute a protected checksum, or generate a key in a

key agreement algorithm. The matching private key is kept secret

by the owner, who uses it to decrypt data, generate a digital

signature, verify a protected checksum, or generate a key in a key

agreement algorithm.

$ key recovery

1. (I) A process for learning the value of a cryptographic key

that was previously used to perform some cryptographic operation.

(See: cryptanalysis.)

2. (I) Techniques that provide an intentional, alternate (i.e.,

secondary) means to access the key used for data confidentiality

service in an encrypted association. [DOD4]

obtaining the key through a key establishment algorithm or

protocol. For the secondary means, there are two classes of key

recovery techniques--key escrow and key encapsulation:

- "Key escrow": A key recovery technique for storing knowledge of

a cryptographic key or parts thereof in the custody of one or

more third parties called "escrow agents", so that the key can

be recovered and used in specified circumstances.

Key escrow is typically implemented with split knowledge

techniques. For example, the Escrowed Encryption Standard

[FP185] entrusts two components of a device-unique split key to

separate escrow agents. The agents provide the components only

to someone legally authorized to conduct electronic

surveillance of telecommunications encrypted by that specific

device. The components are used to reconstruct the device-

unique key, and it is used to obtain the session key needed to

decrypt communications.

- "Key encapsulation": A key recovery technique for storing

knowledge of a cryptographic key by encrypting it with another

key and ensuring that that only certain third parties called

"recovery agents" can perform the decryption operation to

retrieve the stored key.

Key encapsulation typically allows direct retrieval of the

secret key used to provide data confidentiality.

$ key space

(I) The range of possible values of a cryptographic key; or the

number of distinct transformations supported by a particular

cryptographic algorithm. (See: key length.)

$ key translation center

(I) A type of key center (used in a symmetric cryptography) that

implements a key distribution protocol to convey keys between two

(or more) parties who wish to communicate securely. (See: key

distribution center.)

communication between Bob and Alice, who (a) wish to communicate

with each other but do not currently share keys, (b) each share a

KEK with the center, and (c) have the ability to generate or

acquire keys by themselves. Alice generates or acquires a set of

keys for communication with Bob. Alice encrypts the set in the KEK

she shares with the center and sends the encrypted set to the

center. The center decrypts the set, reencrypts the set in the KEK

it shares with Bob, and either sends that encrypted set to Alice

for her to forward to Bob, or sends it directly to Bob (although

direct distribution is not supported in the ANSI standard

[A9017]).

$ key transport (algorithm or protocol)

(I) A key establishment method by which a secret key is generated

by one entity in a communication association and securely sent to

another entity in the association. (See: key agreement.)

(O) "The procedure to send a symmetric key from one party to other

parties. As a result, all legitimate participants share a common

symmetric key in such a way that the symmetric key is determined

entirely by one party." [A9042]

session key and then use the Rivest-Shamir-Adleman algorithm to

encrypt that key with the public key of the intended recipient.

$ key update

(I) Derive a new key from an existing key. (See: certificate

rekey.)

$ key validation

(N) "The procedure for the receiver of a public key to check that

the key conforms to the arithmetic requirements for such a key in

order to thwart certain types of attacks." [A9042]

$ keyed hash

(I) A cryptographic hash (e.g., [R1828]) in which the mapping to a

hash result is varied by a second input parameter that is a

cryptographic key. (See: checksum.)

be correctly computed without knowledge of the secret key. Thus,

the secret key protects the hash result so it can be used as a

checksum even when there is a threat of an active attack on the

data. There are least two forms of keyed hash:

- A function based on a keyed encryption algorithm. (E.g., see:

Data Authentication Code.)

- A function based on a keyless hash that is enhanced by

combining (e.g., by concatenating) the input data object

parameter with a key parameter before mapping to the hash

result. (E.g., see: HMAC.)

$ keying material

(I) Data (such as keys, key pairs, and initialization values)

needed to establish and maintain a cryptographic security

association.

$ KMID

See: key material identifier.

$ known-plaintext attack

(I) A cryptanalysis technique in which the analyst tries to

determine the key from knowledge of some plaintext-ciphertext

pairs (although the analyst may also have other clues, such as the

knowing the cryptographic algorithm).

$ L2F

See: Layer 2 Forwarding Protocol.

$ L2TP

See: Layer 2 Tunneling Protocol.

$ label

See: security label.

$ Language of Temporal Ordering Specification (LOTOS)

(N) A language (ISO 8807-1990) for formal specification of

computer network protocols; describes the order in which events

occur.

$ lattice model

(I) A security model for flow control in a system, based on the

lattice that is formed by the finite security levels in a system

and their partial ordering. [Denn] (See: flow control, security

level, security model.)

set of security levels, such as those used in military

organizations.

its elements such that for every pair of elements there is a least

upper bound and a greatest lower bound. For example, a lattice is

formed by a finite set S of security levels -- i.e., a set S of all

ordered pairs (x, c), where x is one of a finite set X of

hierarchically ordered classification levels (X1, ..., Xm), and c

is a (possibly empty) subset of a finite set C of non-hierarchical

categories (C1, ..., Cn) -- together with the "dominate" relation.

(See: dominate.)

$ Law Enforcement Access Field (LEAF)

(N) A data item that is automatically embedded in data encrypted

by devices (e.g., see: CLIPPER chip) that implement the Escrowed

Encryption Standard.

$ Layer 2 Forwarding Protocol (L2F)

(N) An Internet protocol (originally developed by Cisco

Corporation) that uses tunneling of PPP over IP to create a

virtual extension of a dial-up link across a network, initiated by

the dial-up server and transparent to the dial-up user. (See:

L2TP.)

$ Layer 2 Tunneling Protocol (L2TP)

(N) An Internet client-server protocol that combines aspects of

PPTP and L2F and supports tunneling of PPP over an IP network or

over frame relay or other switched network. (See: virtual private

network.)

L2TP does not specify security services; it depends on protocols

layered above and below it to provide any needed security.

$ LDAP

See: Lightweight Directory Access Protocol.

$ least privilege

(I) The principle that a security architecture should be designed

so that each system entity is granted the minimum system resources

and authorizations that the entity needs to do its work. (See:

economy of mechanism.)

accident, error, or unauthorized act.

$ Lightweight Directory Access Protocol (LDAP)

(N) A client-server protocol that supports basic use of the X.500

Directory (or other directory servers) without incurring the

resource requirements of the full Directory Access Protocol (DAP).

[R1777]

provide simple read/write interactive directory service. Supports

both simple authentication and strong authentication of the client

to the directory server.

$ link

(I) World Wide Web usage: See: hyperlink.

(I) Subnetwork usage: A point-to-point communication channel

connecting two subnetwork relays (especially one between two

packet switches) that is implemented at OSI layer 2. (See: link

encryption.)

If a computer at one end of a link sends a sequence of bits, the

sequence simply arrives at the other end after a finite time,

although some bits may have been changed either accidentally

(errors) or by active wiretapping.

$ link-by-link encryption

$ link encryption

(I) Stepwise protection of data that flows between two points in a

network, provided by encrypting data separately on each network

link, i.e., by encrypting data when it leaves a host or subnetwork

relay and decrypting when it arrives at the next host or relay.

Each link may use a different key or even a different algorithm.

[R1455] (See: end-to-end encryption.)

$ logic bomb

(I) Malicious logic that activates when specified conditions are

met. Usually intended to cause denial of service or otherwise

damage system resources. (See: Trojan horse, virus, worm.)

$ login

(I) The act of a system entity gaining access to a session in

which the entity can use system resources; usually accomplished by

providing a user name and password to an access control system

that authenticates the user.

security events, such as the beginning of sessions, and who

initiates them.

$ LOTOS

See: Language of Temporal Ordering Specification.

$ MAC

See: mandatory access control, Message Authentication Code.

$ malicious logic

(I) Hardware, software, or firmware that is intentionally included

or inserted in a system for a harmful purpose. (See: logic bomb,

Trojan horse, virus, worm.)

$ malware

(I) A contraction of "malicious software". (See: malicious logic.)

(D) ISDs SHOULD NOT use this term because it is not listed in most

dictionaries and could confuse international readers.

$ man-in-the-middle

(I) A form of active wiretapping attack in which the attacker

intercepts and selectively modifies communicated data in order to

masquerade as one or more of the entities involved in a

communication association. (See: hijack attack, piggyback attack.)

key by using the Diffie-Hellman algorithm without data origin

authentication service. A "man in the middle" could (a) block

direct communication between Alice and Bob and then (b) masquerade

as Alice sending data to Bob, (c) masquerade as Bob sending data

to Alice, (d) establish separate session keys with each of them,

and (e) function as a clandestine proxy server between them in

order to capture or modify sensitive information that Alice and

Bob think they are sending only to each other.

$ mandatory access control (MAC)

(I) An access control service that enforces a security policy

based on comparing (a) security labels (which indicate how

sensitive or critical system resources are) with (b) security

clearances (which indicate system entities are eligible to access

certain resources). (See: discretionary access control, rule-based

security policy.)

entity that has clearance to access a resource may not, just by

its own volition, enable another entity to access that resource.

(O) "A means of restricting access to objects based on the

sensitivity (as represented by a label) of the information

contained in the objects and the formal authorization (i.e.,

clearance) of subjects to access information of such sensitivity."

[DOD1]

$ manipulation detection code

(D) ISDs SHOULD NOT use this term as a synonym for "checksum"

because the word "manipulation" implies protection against active

attacks, which an ordinary checksum might not provide. Instead, if

such protection is intended, use "protected checksum" or some

particular type thereof, depending on which is meant. If such

protection is not intended, use "error detection code" or some

specific type of checksum that is not protected.

$ masquerade attack

(I) A type of attack in which one system entity illegitimately

poses as (assumes the identity of) another entity. (See: spoofing

attack.)

$ MCA

See: merchant certificate authority.

$ MD2

(N) A cryptographic hash [R1319] that produces a 128-bit hash

result, was designed by Ron Rivest, and is similar to MD4 and MD5

but slower. (See: message digest.)

$ MD4

(N) A cryptographic hash [R1320] that produces a 128-bit hash

result and was designed by Ron Rivest. (See: message digest and

SHA-1.)

$ MD5

(N) A cryptographic hash [R1321] that produces a 128-bit hash

result and was designed by Ron Rivest to be an improved version of

MD4.

$ merchant

(O) SET usage: "A seller of goods, services, and/or other

information who accepts payment for these items electronically."

[SET2] A merchant may also provide electronic selling services

and/or electronic delivery of items for sale. With SET, the

merchant can offer its cardholders secure electronic interactions,

but a merchant that accepts payment cards is required to have a

relationship with an acquirer. [SET1, SET2]

$ merchant certificate

(O) SET usage: A public-key certificate issued to a merchant.

Sometimes used to refer to a pair of such certificates where one

is for digital signature use and the other is for encryption.

$ merchant certification authority (MCA)

(O) SET usage: A CA that issues digital certificates to merchants

and is operated on behalf of a payment card brand, an acquirer, or

another party according to brand rules. Acquirers verify and

approve requests for merchant certificates prior to issuance by

the MCA. An MCA does not issue a CRL, but does distribute CRLs

issued by root CAs, brand CAs, geopolitical CAs, and payment

gateway CAs. [SET2]

$ mesh PKI

(I) A non-hierarchical PKI architecture in which there are several

trusted CAs rather than a single root. Each certificate user bases

path validations on the public key of one of the trusted CAs,

usually the one that issued that user's own public-key

certificate. Rather than having superior-to-subordinate

relationships between CAs, the relationships are peer-to-peer, and

CAs issue cross-certificates to each other. (See: hierarchical

PKI, trust-file PKI.)

$ message authentication code vs. Message Authentication Code (MAC)

1. (N) Capitalized: "(The) Message Authentication Code" refers to

an ANSI standard for a checksum that is computed with a keyed hash

that is based on DES. [A9009] (Also known as the U.S. Government

standard Data Authentication Code. [FP113])

chaining with IV = 0.

2. (D) Not capitalized: ISDs SHOULD NOT use the uncapitalized form

"message authentication code", because this term mixes concepts in

a potentially misleading way. Instead, use "checksum", "error

detection code", "hash", "keyed hash", "Message Authentication

Code", or "protected checksum", depending on what is meant. (See:

authentication code.)

because it implies that the mechanism is particularly suitable for

or limited to electronic mail (see: Message Handling Systems), the

word "authentication" is misleading because the mechanism

primarily serves a data integrity function rather than an

authentication function, and the word "code" is misleading because

it implies that either encoding or encryption is involved or that

the term refers to computer software.

$ message digest

(D) ISDs SHOULD NOT use this term as a synonym for "hash result"

because it unnecessarily duplicates the meaning of the other, more

general term and mixes concepts in a potentially misleading way.

(See: cryptographic hash, Message Handling System.)

$ Message Handling Systems

(I) A ITU-T/ISO system concept, which encompasses the notion of

electronic mail but defines more comprehensive OSI systems and

services that enable users to exchange messages on a store-and-

forward basis. (The ISO equivalent is "Message Oriented Text

Interchange System".) (See: X.400.)

$ message indicator

(D) ISDs SHOULD NOT use this term as a synonym for "initialization

value" because it mixes concepts in a potentially misleading way.

$ message integrity check

$ message integrity code

(D) ISDs SHOULD NOT use these terms because they mix concepts in a

potentially misleading way. (The word "message" is misleading

because it suggests that the mechanism is particularly suitable

for or limited to electronic mail. The word "code" is misleading

because it suggests that either encoding or encryption is

involved, or that the term refers to computer software.) Instead,

use "checksum", "error detection code", "hash", "keyed hash",

"Message Authentication Code", or "protected checksum", depending

on what is meant.

$ Message Security Protocol (MSP)

(N) A secure message handling protocol [SDNS7] for use with X.400

and Internet mail protocols. Developed by NSA's SDNS program and

used in the U.S. Defense Message System.

$ MHS

See: message handling system.

$ MIME

See: Multipurpose Internet Mail Extensions.

$ MIME Object Security Services (MOSS)

(I) An Internet protocol [R1848] that applies end-to-end

encryption and digital signature to MIME message content, using

symmetric cryptography for encryption and asymmetric cryptography

for key distribution and signature. MOSS is based on features and

specifications of PEM. (See: S/MIME.)

$ Minimum Interoperability Specification for PKI Components (MISPC)

(N) A technical description to provide a basis for interoperation

between PKI components from different vendors; consists primarily

of a profile of certificate and CRL extensions and a set of

transactions for PKI operation. [MISPC]

$ MISPC

See: Minimum Interoperability Specification for PKI Components.

$ MISSI

(N) Multilevel Information System Security Initiative, an NSA

program to encourage development of interoperable, modular

products for constructing secure network information systems in

support of a wide variety of Government missions. (See: MSP.)

$ MISSI user

(O) MISSI usage: A system entity that is the subject of one or

more MISSI X.509 public-key certificates issued under a MISSI

certification hierarchy. (See: personality.)

issue certificates. A MISSI user is usually a person but may be a

machine or other automated process. Some machines are required to

operate non-stop. To avoid downtime needed to exchange the

FORTEZZA cards of machine operators at shift changes, the machines

may be issued their own cards, as if they were persons.

$ mode

$ mode of operation

(I) Encryption usage: A technique for enhancing the effect of a

cryptographic algorithm or adapting the algorithm for an

application, such as applying a block cipher to a sequence of data

blocks or a data stream. (See: electronic codebook, cipher block

chaining, cipher feedback, output feedback.)

(I) System operation usage: A type of security policy that states

the range of classification levels of information that a system is

permitted to handle and the range of clearances and authorizations

of users who are permitted to access the system. (See: dedicated

security mode, multilevel security mode, partitioned security

mode, system high security mode.)

$ modulus

(I) The defining constant in modular arithmetic, and usually a

part of the public key in asymmetric cryptography that is based on

modular arithmetic. (See: Diffie-Hellman, Rivest-Shamir-Adleman.)

$ Morris Worm

(I) A worm program written by Robert T. Morris, Jr. that flooded

the ARPANET in November, 1988, causing problems for thousands of

hosts. (See: worm.)

$ MOSS

See: MIME Object Security Services.

$ MSP

See: Message Security Protocol.

$ multilevel secure (MLS)

(I) A class of system that has system resources (particularly

stored information) at more than one security level (i.e., has

different types of sensitive resources) and that permits

concurrent access by users who differ in security clearance and

need-to-know, but is able to prevent each user from accessing

resources for which the user lacks authorization.

$ multilevel security mode

(I) A mode of operation of an information system, that allows two

or more classification levels of information to be processed

concurrently within the same system when not all users have a

clearance or formal access authorization for all data handled by

the system.

policy regarding system accreditation [DOD2], but the term is also

used outside the Defense Department and outside the Government.

$ Multipurpose Internet Mail Extensions (MIME)

(I) An Internet protocol [R2045] that enhances the basic format of

Internet electronic mail messages [R0822] to be able to use

character sets other than US-ASCII for textual headers and text

content, and to carry non-textual and multi-part content. (See:

S/MIME.)

$ mutual suspicion

(I) The state that exists between two interacting system entities

in which neither entity can trust the other to function correctly

with regard to some security requirement.

$ National Computer Security Center (NCSC)

(N) A U.S. Department of Defense organization, housed in NSA, that

has responsibility for encouraging widespread availability of

trusted computer systems throughout the Federal Government. It has

established criteria for, and performs evaluations of, computer

and network systems that have a trusted computing base. (See:

Evaluated Products List, Rainbow Series, TCSEC.)

$ National Information Assurance Partnership (NIAP)

(N) An organization created by NIST and NSA to enhance the quality

of commercial products for information security and increase

consumer confidence in those products through objective evaluation

and testing methods.

a National Performance Review Reinvention Laboratory. NIAP

functions include the following:

- Developing tests, test methods, and other tools that developers

and testing laboratories may use to improve and evaluate

security products.

- Collaborating with industry and others on research and testing

programs.

- Using the Common Criteria to develop protection profiles and

associated test sets for security products and systems.

- Cooperating with the NIST National Voluntary Laboratory

Accreditation Program to develop a program to accredit private-

sector laboratories for the testing of information security

products using the Common Criteria.

- Working to establish a formal, international mutual recognition

scheme for a Common Criteria-based evaluation.

$ National Institute of Standards and Technology (NIST)

(N) A U.S. Department of Commerce agency that promotes U.S.

economic growth by working with industry to develop and apply

technology, measurements, and standards. Has primary Government

responsibility for INFOSEC standards for unclassified but

sensitive information. (See: ANSI, DES, DSA, DSS, FIPS, NIAP,

NSA.)

$ National Security Agency (NSA)

(N) A U.S. Department of Defense intelligence agency that has

primary Government responsibility for INFOSEC for classified

information and for unclassified but sensitive information handled

by national security systems. (See: FORTEZZA, KEA, MISSI, NIAP,

NIST, SKIPJACK.)

$ need-to-know

(I) The necessity for access to, knowledge of, or possession of

specific information required to carry out official duties.

custodian of sensitive information, prior to disclosing the

information to someone else, to establish that the intended

recipient has proper authorization to access the information.

$ network

See: computer network.

$ NIAP

See: National Information Assurance Partnership.

$ NIST

See: National Institute of Standards and Technology.

$ NLSP

Network Layer Security Protocol. An OSI protocol (IS0 11577) for

end-to-end encryption services at the top of OSI layer 3. NLSP is

derived from an SDNS protocol, SP3, but is much more complex.

$ no-lone zone

(I) A room or other space to which no person may have

unaccompanied access and that, when occupied, is required to be

occupied by two or more appropriately authorized persons. (See:

dual control.)

$ nonce

(I) A random or non-repeating value that is included in data

exchanged by a protocol, usually for the purpose of guaranteeing

liveness and thus detecting and protecting against replay attacks.

$ non-critical

See: critical (extension of certificate).

$ non-repudiation service

(I) A security service that provide protection against false

denial of involvement in a communication. (See: repudiation.)

from repudiating a communication. Instead, the service provides

evidence that can be stored and later presented to a third party

to resolve disputes that arise if and when a communication is

repudiated by one of the entities involved. There are two basic

kinds of non-repudiation service:

- "Non-repudiation with proof of origin" provides the recipient

of data with evidence that proves the origin of the data, and

thus protects the recipient against an attempt by the

originator to falsely deny sending the data. This service can

be viewed as a stronger version of an data origin

authentication service, in that it proves authenticity to a

third party.

- "Non-repudiation with proof of receipt" provides the originator

of data with evidence that proves the data was received as

addressed, and thus protects the originator against an attempt

by the recipient to falsely deny receiving the data.

the term "critical action" to refer to the act of communication

that is the subject of the service:

-------- -------- -------- -------- -------- . --------

Phase 1: Phase 2: Phase 3: Phase 4: Phase 5: . Phase 6:

Request Generate Transfer Verify Retain . Resolve

Service Evidence Evidence Evidence Evidence . Dispute

-------- -------- -------- -------- -------- . --------

Service Critical Evidence Evidence Archive . Evidence

Request => Action => Stored => Is => Evidence . Is

Is Made Occurs For Later Tested In Case . Verified

and Use ^ Critical . ^

Evidence v Action Is .

Is +-------------------+ Repudiated .

Generated Verifiable Evidence------> ... . ----+

+-------------------+

Phase / Explanation

-------------------

1. Before the critical action, the service requester asks, either

implicitly or explicitly, to have evidence of the action be

generated.

2. When the critical action occurs, evidence is generated by a

process involving the potential repudiator and possibly also a

trusted third party.

3. The evidence is transferred to the requester, or stored by a

third party, for later use if needed.

4. The entity that holds the evidence tests to be sure that it

will suffice if a dispute arises.

5. The evidence is retained for possible future retrieval and use.

6. In this phase, which occurs only if the critical action is

repudiated, the evidence is retrieved from storage, presented,

and verified to resolve the dispute.

$ no-PIN ORA (NORA)

(O) MISSI usage: An organizational RA that operates in a mode in

which the ORA performs no card management functions and,

therefore, does not require knowledge of either the SSO PIN or

user PIN for an end user's FORTEZZA PC card.

$ NORA

See: no-PIN ORA.

$ notarization

(I) Registration of data under the authority or in the care of a

trusted third party, thus making it possible to provide subsequent

assurance of the accuracy of characteristics claimed for the data,

such as content, origin, time, and delivery. [I7498 Part 2] (See:

digital notary.)

$ NULL encryption algorithm

(I) An algorithm [R2410] that does nothing to transform plaintext

data; i.e., a no-op. It originated because of IPsec ESP, which

always specifies the use of an encryption algorithm to provide

confidentiality. The NULL encryption algorithm is a convenient way

to represent the option of not applying encryption in ESP (or in

any other context where this is needed).

$ OAKLEY

(I) A key establishment protocol (proposed for IPsec but

superseded by IKE) based on the Diffie-Hellman algorithm and

designed to be a compatible component of ISAKMP. [R2412]

and associated authenticated identities for parties. I.e., OAKLEY

provides authentication service to ensure the entities of each

other's identity, even if the Diffie-Hellman exchange is

threatened by active wiretapping. Also, provides public-key

forward secrecy for the shared key and supports key updates,

incorporation of keys distributed by out-of-band mechanisms, and

user-defined abstract group structures for use with Diffie-

Hellman.

$ object

(I) Trusted computer system modeling usage: A system element that

contains or receives information. (See: Bell-LaPadula Model,

trusted computer system.)

$ object identifier (OID)

(I) An official, globally unique name for a thing, written as a

sequence of integers (which are formed and assigned as defined in

the ASN.1 standard) and used to reference the thing in abstract

specifications and during negotiation of security services in a

protocol.

(O) "A value (distinguishable from all other such values) which is

associated with an object." [X680]

(which is similar to but different from the X.500 Directory

Information Tree). Each arc (i.e., each branch of the tree) is

labeled with a non-negative integer. An OID is the sequence of

integers on the path leading from the root of the tree to a named

object.

for use by ITU-T, {1} for use by ISO, and {2} for use by both

jointly. Below ITU-T are four arcs, where {0 0} is for ITU-T

recommendations. Below {0 0} are 26 arcs, one for each series of

recommendations starting with the letters A to Z, and below these

are arcs for each recommendation. Thus, the OID for ITU-T

Recommendation X.509 is {0 0 24 509}. Below ISO are four arcs,

where {1 0 }is for ISO standards, and below these are arcs for

each ISO standard. Thus, the OID for ISO/IEC 9594-8 (the ISO

number for X.509) is {1 0 9594 8}.

organization names below the branch {joint-iso-ccitt(2)

country(16) US(840) organization(1)}. The NIST CSOR records PKI

objects below the branch {joint-iso-ccitt(2) country(16) us(840)

gov(101) csor(3) pki(4)}. The U.S. Department of Defense registers

INFOSEC objects below the branch {joint-iso-ccitt(2) country(16)

us(840) organization(1) gov(101) dod(2) infosec(1)}. The OID for

the PKIX private extension is defined in an arc below the arc for

the PKIX name space, as {iso(1) identified-organization(3) dod(6)

internet(1) security(5) mechanisms(5) pkix(7) 1 1}.

$ object reuse

(N) "The reassignment and reuse of a storage medium (e.g., page

frame, disk sector, magnetic tape) that once contained one or more

[information] objects. To be securely reused and assigned to a new

subject, storage media must contain no residual data (magnetic

remanence) from the object(s) previously contained in the media."

[NCS04]

$ OCSP

See: On-line Certificate Status Protocol.

$ octet

(I) A data unit of eight bits. (See: byte.)

in preference to "byte", because some systems use "byte" for data

storage units of a size other than eight.

$ OFB

See: output feedback.

$ ohnosecond

private key has been compromised.

$ OID

See: object identifier.

$ On-line Certificate Status Protocol (OCSP)

(I) An Internet protocol used by a client to obtain from a server

the validity status and other information concerning a digital

certificate.

commercial transactions, it may be necessary to obtain certificate

revocation status that is more timely than is possible with CRLs

or to obtain other kinds of status information. OCSP may be used

to determine the current revocation status of a digital

certificate, in lieu of or as a supplement to checking against a

periodic CRL. An OCSP client issues a status request to an OCSP

server and suspends acceptance of the certificate in question

until the server provides a response.

$ one-time pad

(I) An encryption algorithm in which the key is a random sequence

of symbols and each symbol is used for encryption only one time--

to encrypt only one plaintext symbol to produce only one

ciphertext symbol--and a copy of the key is used similarly for

decryption.

encryption is destroyed after use, as is the copy used for

decryption. This is the only encryption algorithm that is truly

unbreakable, even given unlimited resources for cryptanalysis

[Schn], but key management costs and synchronization problems make

it impractical except in special situations.

$ one-time password

$ One-Time Password (OTP)

1. Not capitalized: A "one-time password" is a simple

authentication technique in which each password is used only once

as authentication information that verifies an identity. This

technique counters the threat of a replay attack that uses

passwords captured by wiretapping.

2. Capitalized: "One-Time Password" is an Internet protocol

[R1938] that is based on S/KEY and uses a cryptographic hash

function to generate one-time passwords for use as authentication

information in system login and in other processes that need

protection against replay attacks.

$ one-way encryption

(I) Irreversible transformation of plaintext to ciphertext, such

that the plaintext cannot be recovered from the ciphertext by

other than exhaustive procedures even if the cryptographic key is

known. (See: encryption.)

$ one-way function

(I) "A (mathematical) function, f, which is easy to compute, but

which for a general value y in the range, it is computationally

difficult to find a value x in the domain such that f(x) = y.

There may be a few values of y for which finding x is not

computationally difficult." [X509]

(D) ISDs SHOULD NOT use this term as a synonym for "cryptographic

hash".

$ open security environment

(O) U.S. Department of Defense usage: A system environment that

meets at least one of the following conditions: (a) Application

developers (including maintainers) do not have sufficient

clearance or authorization to provide an acceptable presumption

that they have not introduced malicious logic. (b) Configuration

control does not provide sufficient assurance that applications

and the equipment are protected against the introduction of

malicious logic prior to and during the operation of system

applications. [NCS04] (See: closed security environment.)

$ Open Systems Interconnection (OSI) Reference Model (OSIRM)

(N) A joint ISO/ITU-T standard [I7498 Part 1] for a seven-layer,

architectural communication framework for interconnection of

computers in networks.

mostly incompatible with the Internet Protocol Suite, but also

include security models, such as X.509, that are used in the

Internet.

(6) Presentation, (5) Session, (4) Transport, (3) Network, (2)

Data Link, and (1) Physical. In this Glossary, these layers are

referred to by number to avoid confusing them with Internet

Protocol Suite layers, which are referred to by name.

the seven deadly sins:

7. Wrath: Application is always angry at the mess it sees below

itself. (Hey! Who is it to be pointing fingers?)

6. Sloth: Presentation is too lazy to do anything productive by

itself.

5. Lust: Session is always craving and demanding what truly

belongs to Application's functionality.

4. Avarice: Transport wants all of the end-to-end functionality.

(Of course, it deserves it, but life isn't fair.)

3. Gluttony: (Connection-Oriented) Network is overweight and

overbearing after trying too often to eat Transport's lunch.

2. Envy: Poor Data Link is always starved for attention. (With

Asynchronous Transfer Mode, maybe now it is feeling less

neglected.)

1. Pride: Physical has managed to avoid much of the controversy,

and nearly all of the embarrassment, suffered by the others.

to Snow White's dwarf friends:

7. Doc: Application acts as if it is in charge, but sometimes

muddles its syntax.

6. Sleepy: Presentation is indolent, being guilty of the sin of

Sloth.

5. Dopey: Session is confused because its charter is not very

clear.

4. Grumpy: Transport is irritated because Network has encroached

on Transport's turf.

3. Happy: Network smiles for the same reason that Transport is

irritated.

2. Sneezy: Data Link makes loud noises in the hope of attracting

attention.

1. Bashful: Physical quietly does its work, unnoticed by the

others.

$ operational integrity

(I) A synonym for "system integrity"; emphasizes the actual

performance of system functions rather than just the ability to

perform them.

$ operations security (OPSEC)

(I) A process to identify, control, and protect evidence of the

planning and execution of sensitive activities and operations, and

thereby prevent potential adversaries from gaining knowledge of

capabilities and intentions.

$ OPSEC

See: operations security.

$ ORA

See: organizational registration authority.

$ Orange Book

(D) ISDs SHOULD NOT use this term as a synonym for "Trusted

Computer System Evaluation Criteria" [CSC001, DOD1]. Instead, use

the full, proper name of the document or, in subsequent

references, the abbreviation "TCSEC". (See: (usage note under)

Green Book.)

$ organizational certificate

(O) MISSI usage: A type of MISSI X.509 public-key certificate that

is issued to support organizational message handling for the U.S.

Government's Defense Message System.

$ organizational registration authority (ORA)

(I) General usage: An RA for an organization.

(O) MISSI usage: The MISSI implementation of RA. A MISSI end

entity that (a) assists a PCA, CA, or SCA to register other end

entities, by gathering, verifying, and entering data and

forwarding it to the signing authority and (b) may also assist

with card management functions. An ORA is a local administrative

authority, and the term refers both to the Office or role, and to

the person who fills that office. An ORA does not sign

certificates, CRLs, or CKLs. (See: no-PIN ORA, SSO-PIN ORA, user-

PIN ORA.)

$ origin authentication

$ origin authenticity

(D) ISDs SHOULD NOT use these terms because they look like

careless use of an internationally standardized term. Instead, use

"data origin authentication" or "peer entity authentication",

depending which is meant.

$ OSI

$ OSIRM

See: Open Systems Interconnection Reference Model.

$ OTP

See: One-Time Password.

$ out of band

(I) Transfer of information using a channel that is outside (i.e.,

separate from) the channel that is normally used. (See: covert

channel.)

secrets (e.g., a symmetric key) or other sensitive information

items (e.g., a root key) that are needed to initialize or

otherwise enable the operation of cryptography or other security

mechanisms. (See: key distribution.)

$ output feedback (OFB)

(N) A block cipher mode [FP081] that modifies electronic codebook

mode to operate on plaintext segments of variable length less than

or equal to the block length.

previously generated output block as the algorithm's next input

block (i.e., by "feeding back" the output block) and combining

(exclusive OR-ing) the output block with the next plaintext

segment (of block length or less) to form the next ciphertext

segment.

$ outside attack

$ outsider attack

See: (secondary definition under) attack.

$ P1363

See: IEEE P1363.

$ PAA

See: policy approving authority.

$ packet filter

See: (secondary definition under) filtering router.

$ pagejacking

(I) A contraction of "Web page hijacking". A masquerade attack in

which the attacker copies (steals) a home page or other material

from the target server, rehosts the page on a server the attacker

controls, and causes the rehosted page to be indexed by the major

Web search services, thereby diverting browsers from the target

server to the attacker's server.

(D) ISDs SHOULD NOT use this term without including a definition,

because the term is not listed in most dictionaries and could

confuse international readers. (See: (usage note under) Green

Book.)

$ PAN

See: primary account number.

$ PAP

See: Password Authentication Protocol.

$ partitioned security mode

(N) A mode of operation of an information system, wherein all

users have the clearance, but not necessarily formal access

authorization and need-to-know, for all information handled by the

system. This mode is defined in U.S. Department of Defense policy

regarding system accreditation. [DoD2]

$ passive attack

See: (secondary definition under) attack.

$ passive wiretapping

See: (secondary definition under) wiretapping.

$ password

(I) A secret data value, usually a character string, that is used

as authentication information. (See: challenge-response.)

explicitly presented in the authentication process, but in some

cases the identity may be implicit.

the password is known only by the system entity whose identity is

being authenticated. Therefore, in a network environment where

wiretapping is possible, simple authentication that relies on

transmission of static (i.e., repetitively used) passwords as

cleartext is inadequate. (See: one-time password, strong

authentication.)

$ Password Authentication Protocol (PAP)

(I) A simple authentication mechanism in PPP. In PAP, a user

identifier and password are transmitted in cleartext. [R1334]

(See: CHAP.)

$ password sniffing

(I) Passive wiretapping, usually on a local area network, to gain

knowledge of passwords. (See: (usage note under) sniffing.)

$ path discovery

(I) For a digital certificate, the process of finding a set of

public-key certificates that comprise a certification path from a

trusted key to that specific certificate.

$ path validation

(I) The process of validating (a) all of the digital certificates

in a certification path and (b) the required relationships between

those certificates, thus validating the contents of the last

certificate on the path. (See: certificate validation.)

$ payment card

(N) SET usage: Collectively refers "to credit cards, debit cards,

charge cards, and bank cards issued by a financial institution and

which reflects a relationship between the cardholder and the

financial institution." [SET2]

$ payment gateway

(O) SET usage: A system operated by an acquirer, or a third party

designated by an acquirer, for the purpose of providing electronic

commerce services to the merchants in support of the acquirer, and

which interfaces to the acquirer to support the authorization,

capture, and processing of merchant payment messages, including

payment instructions from cardholders. [SET1, SET2]

$ payment gateway certification authority (SET PCA)

(O) SET usage: A CA that issues digital certificates to payment

gateways and is operated on behalf of a payment card brand, an

acquirer, or another party according to brand rules. A SET PCA

issues a CRL for compromised payment gateway certificates. [SET2]

(See: PCA.)

$ PC card

(N) A type of credit card-sized, plug-in peripheral device that

was originally developed to provide memory expansion for portable

computers, but is also used for other kinds of functional

expansion. (See: FORTEZZA, PCMCIA.)

form factor in three standard sizes--Types I, II and III--each of

which have a 68-pin interface between the card and the socket into

which it plugs. All three types have the same length and width,

roughly the size of a credit card, but differ in their thickness

from 3.3 to 10.5 mm. Examples include storage modules, modems,

device interface adapters, and cryptographic modules.

$ PCA

(D) ISDs SHOULD NOT use this acronym without a qualifying

adjective because that would be ambiguous. (See: Internet policy

certification authority, (MISSI) policy creation authority, (SET)

payment gateway certification authority.)

$ PCMCIA

(N) Personal Computer Memory Card International Association, a

group of manufacturers, developers, and vendors, founded in 1989

to standardize plug-in peripheral memory cards for personal

computers and now extended to deal with any technology that works

in the PC card form factor. (See: PC card.)

$ peer entity authentication

(I) "The corroboration that a peer entity in an association is the

one claimed." [I7498 Part 2] (See: authentication.)

$ peer entity authentication service

(I) A security service that verifies an identity claimed by or for

a system entity in an association. (See: authentication,

authentication service.)

during, an association to confirm the identity of one entity to

another, thus protecting against a masquerade by the first entity.

However, unlike data origin authentication service, this service

requires an association to exist between the two entities, and the

corroboration provided by the service is valid only at the current

time that the service is provided.

authentication services" under data integrity service.

$ PEM

See: Privacy Enhanced Mail.

$ penetration

(I) Successful, repeatable, unauthorized access to a protected

system resource. (See: attack, violation.)

$ penetration test

(I) A system test, often part of system certification, in which

evaluators attempt to circumvent the security features of the

system. [NCS04]

and conditions. However, for a TCSEC evaluation, testers are

assumed to have all system design and implementation

documentation, including source code, manuals, and circuit

diagrams, and to work under no greater constraints than those

applied to ordinary users.

$ perfect forward secrecy

See: (discussion under) public-key forward secrecy.

$ perimeter

See: security perimeter.

$ periods processing

(I) A mode of system operation in which information of different

sensitivities is processed at distinctly different times by the

same system, with the system being properly purged or sanitized

between periods. (See: color change.)

$ permission

(I) A synonym for "authorization", but "authorization" is

preferred in the PKI context. (See: privilege.)

$ personal identification number (PIN)

(I) A character string used as a password to gain access to a

system resource. (See: authentication information.)

serves as a user identifier, and a PIN's characters are not

necessarily all numeric. A better name for this concept would have

been "personal authentication system string (PASS)".

FORTEZZA PC card's use up to 12 characters for user or SSO PINs.

$ personality

$ personality label

(O) MISSI usage: A set of MISSI X.509 public-key certificates that

have the same subject DN, together with their associated private

keys and usage specifications, that is stored on a FORTEZZA PC

card to support a role played by the card's user.

aware application, the data determines behavior traits (the

personality) of the application. A card's user may have multiple

personalities on the card. Each has a "personality label", a user-

friendly character string that applications can display to the

user for selecting or changing the personality to be used. For

example, a military user's card might contain three personalities:

GENERAL HALFTRACK, COMMANDER FORT SWAMPY, and NEW YEAR'S EVE PARTY

CHAIRMAN. Each personality includes one or more certificates of

different types (such as DSA versus RSA), for different purposes

(such as digital signature versus encryption), or with different

authorizations.

$ personnel security

(I) Procedures to ensure that persons who access a system have

proper clearance, authorization, and need-to-know as required by

the system's security policy.

$ PGP(trademark)

See: Pretty Good Privacy.

$ Photuris

(I) A UDP-based, key establishment protocol for session keys,

designed for use with the IPsec protocols AH and ESP. Superseded

by IKE.

$ phreaking

(I) A contraction of "telephone breaking". An attack on or

penetration of a telephone system or, by extension, any other

communication or information system. [Raym]

(D) ISDs SHOULD NOT use this term because it is not listed in most

dictionaries and could confuse international readers.

$ physical security

(I) Tangible means of preventing unauthorized physical access to a

system. E.g., fences, walls, and other barriers; locks, safes, and

vaults; dogs and armed guards; sensors and alarm bells. [FP031,

R1455]

$ piggyback attack

(I) A form of active wiretapping in which the attacker gains

access to a system via intervals of inactivity in another user's

legitimate communication connection. Sometimes called a "between-

the-lines" attack. (See: hijack attack, man-in-the-middle attack.)

$ PIN

See: personal identification number.

$ ping of death

(I) An attack that sends an improperly large ICMP [R0792] echo

request packet (a "ping") with the intent of overflowing the input

buffers of the destination machine and causing it to crash.

$ ping sweep

(I) An attack that sends ICMP [R0792] echo requests ("pings") to a

range of IP addresses, with the goal of finding hosts that can be

probed for vulnerabilities.

$ PKCS

See: Public-Key Cryptography Standards.

$ PKCS #7

(N) A standard [PKC07, R2315] from the PKCS series; defines a

syntax for data that may have cryptography applied to it, such as

for digital signatures and digital envelopes.

$ PKCS #10

(N) A standard [PKC10] from the PKCS series; defines a syntax for

requests for public-key certificates. (See: certification

request.)

contain other attributes, and is signed by the entity making the

request. The request is sent to a CA, who converts it to an X.509

public-key certificate (or some other form) and returns it,

possibly in PKCS #7 format.

$ PKCS #11

(N) A standard [PKC11] from the PKCS series; defines a software

CAPI called Cryptoki (pronounced "crypto-key"; short for

"cryptographic token interface") for devices that hold

cryptographic information and perform cryptographic functions.

$ PKI

See: public-key infrastructure.

$ PKIX

(I) (1.) A contraction of "Public-Key Infrastructure (X.509)", the

name of the IETF working group that is specifying an architecture

and set of protocols needed to support an X.509-based PKI for the

Internet. (2.) A collective name for that architecture and set of

protocols.

certificates in multiple Internet applications and to promote

interoperability between different implementations that use those

certificates. The resulting PKI is intended to provide a framework

that supports a range of trust and hierarchy environments and a

range of usage environments. PKIX specifies (a) profiles of the v3

X.509 public-key certificate standards and the v2 X.509 CRL

standards for the Internet; (b) operational protocols used by

relying parties to obtain information such as certificates or

certificate status; (c) management protocols used by system

entities to exchange information needed for proper management of

the PKI; and (d) information about certificate policies and CPSs,

covering the areas of PKI security not directly addressed in the

rest of PKIX.

$ PKIX private extension

(I) PKIX defines a private extension to identify an on-line

verification service supporting the issuing CA.

$ plaintext

(I) Data that is input to and transformed by an encryption

process, or that is output by a decryption process.

cleartext. But in some cases, the input is ciphertext that was

output from another encryption operation. (See: superencryption.)

$ Point-to-Point Protocol (PPP)

(I) An Internet Standard protocol [R1661] for encapsulation and

full-duplex transportation of network layer (mainly OSI layer 3)

protocol data packets over a link between two peers, and for

multiplexing different network layer protocols over the same link.

Includes optional negotiation to select and use a peer entity

authentication protocol to authenticate the peers to each other

before they exchange network layer data. (See: CHAP, EAP, PAP.)

$ Point-to-Point Tunneling Protocol (PPTP)

(I) An Internet client-server protocol (originally developed by

Ascend and Microsoft) that enables a dial-up user to create a

virtual extension of the dial-up link across a network by

tunneling PPP over IP. (See: L2TP.)

protocol (or OSI layer 3 protocol). Therefore, PPTP does not

specify security services; it depends on protocols above and below

it to provide any needed security. PPTP makes it possible to

divorce the location of the initial dial-up server (i.e., the PPTP

Access Concentrator, the client, which runs on a special-purpose

host) from the location at which the dial-up protocol (PPP)

connection is terminated and access to the network is provided

(i.e., the PPTP Network Server, which runs on a general-purpose

host).

$ policy

(D) ISDs SHOULD NOT use this word as an abbreviation for either

"security policy" or "certificate policy". Instead, to avoid

misunderstanding, use the fully qualified term, at least at the

point of first usage.

$ policy approving authority (PAA)

(O) MISSI usage: The top-level signing authority of a MISSI

certification hierarchy. The term refers both to that

authoritative office or role and to the person who plays that

role. (See: root registry.)

certificates. A PAA issues CRLs but does not issue a CKL. A PAA

may issue cross-certificates to other PAAs.

$ policy certification authority (Internet PCA)

(I) An X.509-compliant CA at the second level of the Internet

certification hierarchy, under the Internet Policy Registration

Authority (IPRA). Each PCA operates in accordance with its

published security policy (see: certification practice statement)

and within constraints established by the IPRA for all PCAs.

[R1422]. (See: policy creation authority.)

$ policy creation authority (MISSI PCA)

(O) MISSI usage: The second level of a MISSI certification

hierarchy; the administrative root of a security policy domain of

MISSI users and other, subsidiary authorities. The term refers

both to that authoritative office or role and to the person who

fills that office. (See: policy certification authority.)

authority. The PCA registers the CAs in its domain, defines their

configurations, and issues their X.509 public-key certificates.

(The PCA may also issue certificates for SCAs, ORAs, and other end

entities, but a PCA does not usually do this.) The PCA

periodically issues CRLs and CKLs for its domain.

$ Policy Management Authority

(N) Canadian usage: An organization responsible for PKI oversight

and policy management in the Government of Canada.

$ policy mapping

(I) "Recognizing that, when a CA in one domain certifies a CA in

another domain, a particular certificate policy in the second

domain may be considered by the authority of the first domain to

be equivalent (but not necessarily identical in all respects) to a

particular certificate policy in the first domain." [X509]

$ POP3

See: Post Office Protocol, version 3.

$ POP3 APOP

(I) A POP3 "command" (better described as a transaction type, or a

protocol-within-a-protocol) by which a POP3 client optionally uses

a keyed hash (based on MD5) to authenticate itself to a POP3

server and, depending on the server implementation, to protect

against replay attacks. (See: CRAM, POP3 AUTH, IMAP4

AUTHENTICATE.)

client. The subsequent APOP command sent by the client to the

server contains the client's name and the hash result of applying

MD5 to a string formed from both the timestamp and a shared secret

that is known only to the client and the server. APOP was designed

to provide as an alternative to using POP3's USER and PASS (i.e.,

password) command pair, in which the client sends a cleartext

password to the server.

$ POP3 AUTH

(I) A "command" [R1734] (better described as a transaction type,

or a protocol-within-a-protocol) in POP3, by which a POP3 client

optionally proposes a mechanism to a POP3 server to authenticate

the client to the server and provide other security services.

(See: POP3 APOP, IMAP4 AUTHENTICATE.)

performing a challenge-response authentication protocol and,

optionally, negotiating a protection mechanism for subsequent POP3

interactions. The security mechanisms used by POP3 AUTH are those

used by IMAP4.

$ port scan

(I) An attack that sends client requests to a range of server port

addresses on a host, with the goal of finding an active port and

exploiting a known vulnerability of that service.

$ POSIX

(N) Portable Operating System Interface for Computer Environments,

a standard [FP151, IS9945-1] (originally IEEE Standard P1003.1)

that defines an operating system interface and environment to

support application portability at the source code level. It is

intended to be used by both application developers and system

implementers.

UNIX systems, including discretionary access control and

privilege. IEEE Draft Standard P1003.6.1 specifies additional

functionality not provided in the base standard, including (a)

discretionary access control, (b) audit trail mechanisms, (c)

privilege mechanisms, (d) mandatory access control, and (e)

information label mechanisms.

$ Post Office Protocol, version 3 (POP3)

(I) An Internet Standard protocol [R1939] by which a client

workstation can dynamically access a mailbox on a server host to

retrieve mail messages that the server has received and is holding

for the client. (See: IMAP4.)

a server and providing other security services. (See: POP3 APOP,

POP3 AUTH.)

$ PPP

See: Point-to-Point Protocol.

$ PPTP

See: Point-to-Point Tunneling Protocol.

$ pre-authorization

(I) A capability of a CAW that enables certification requests to

be automatically validated against data provided in advance to the

CA by an authorizing entity.

$ Pretty Good Privacy(trademark) (PGP(trademark))

(O) Trademarks of Network Associates, Inc., referring to a

computer program (and related protocols) that uses cryptography to

provide data security for electronic mail and other applications

on the Internet. (See: MOSS, PEM, S/MIME.)

IDEA keys by encrypting them with RSA, and creates digital

signatures on messages with MD5 and RSA. To establish ownership of

public keys, PGP depends on the web of trust. (See: Privacy

Enhanced Mail.)

$ primary account number (PAN)

(O) SET usage: "The assigned number that identifies the card

issuer and cardholder. This account number is composed of an

issuer identification number, an individual account number

identification, and an accompanying check digit as defined by ISO

7812-1985." [SET2, IS7812] (See: bank identification number.)

based credit card. The PAN identifies the issuer to which a

transaction is to be routed and the account to which it is to be

applied unless specific instructions indicate otherwise. The

authority that assigns the bank identification number part of the

PAN is the American Bankers Association.

$ privacy

(I) The right of an entity (normally a person), acting in its own

behalf, to determine the degree to which it will interact with its

environment, including the degree to which the entity is willing

to share information about itself with others. (See: anonymity.)

(O) "The right of individuals to control or influence what

information related to them may be collected and stored and by

whom and to whom that information may be disclosed." [I7498 Part

(D) ISDs SHOULD NOT use this term as a synonym for "data

confidentiality" or "data confidentiality service", which are

different concepts. Privacy is a reason for security rather than a

kind of security. For example, a system that stores personal data

needs to protect the data to prevent harm, embarrassment,

inconvenience, or unfairness to any person about whom data is

maintained, and to protect the person's privacy. For that reason,

the system may need to provide data confidentiality service.

$ Privacy Enhanced Mail (PEM)

(I) An Internet protocol to provide data confidentiality, data

integrity, and data origin authentication for electronic mail.

[R1421, R1422]. (See: MOSS, MSP, PGP, S/MIME.)

distribution of DES keys by encrypting them with RSA, and signs

messages with RSA over either MD2 or MD5. To establish ownership

of public keys, PEM uses a certification hierarchy, with X.509

public-key certificates and X.509 CRLs that are signed with RSA

and MD2. (See: Pretty Good Privacy.)

management methods, but is limited to specifying security services

only for text messages and, like MOSS, has not been widely

implemented in the Internet.

$ private component

(I) A synonym for "private key".

(D) In most cases, ISDs SHOULD NOT use this term; to avoid

confusing readers, use "private key" instead. However, the term

MAY be used when specifically discussing a key pair; e.g., "A key

pair has a public component and a private component."

$ private extension

See: (secondary definition under) extension.

$ private key

(I) The secret component of a pair of cryptographic keys used for

asymmetric cryptography. (See: key pair, public key.)

(O) "(In a public key cryptosystem) that key of a user's key pair

which is known only by that user." [X509]

$ privilege

(I) An authorization or set of authorizations to perform security-

relevant functions, especially in the context of a computer

operating system.

$ privilege management infrastructure

(N) "The complete set of processes required to provide an

authorization service", i.e., processes concerned with attribute

certificates. [FPDAM] (See: PKI.)

(D) ISDs SHOULD NOT use this term and its definition because the

definition is vague, and there is no consensus on an alternate

definition.

$ privileged process

(I) An computer process that is authorized (and, therefore,

trusted) to perform some security-relevant functions that ordinary

processes are not. (See: privilege, trusted process.)

$ procedural security

(D) ISDs SHOULD NOT use this term as a synonym for "administrative

security". Any type of security may involve procedures; therefore,

the term may be misleading. Instead, use "administrative

security", "communication security", "computer security",

"emanations security", "personnel security", "physical security",

or whatever specific type is meant. (See: security architecture.)

$ proprietary

(I) Refers to information (or other property) that is owned by an

individual or organization and for which the use is restricted by

that entity.

$ protected checksum

(I) A checksum that is computed for a data object by means that

protect against active attacks that would attempt to change the

checksum to make it match changes made to the data object. (See:

digital signature, keyed hash, (discussion under) checksum.

$ protected distribution system

(I) A wireline or fiber-optic system that includes sufficient

safeguards (acoustic, electric, electromagnetic, and physical) to

permit its use for unencrypted transmission of (cleartext) data.

$ protection authority

See: (secondary definition under) Internet Protocol Security

Option.

$ protection ring

(I) One of a hierarchy of privileged operation modes of a system

that gives certain access rights to processes authorized to

operate in that mode.

$ protocol

(I) A set of rules (i.e., formats and procedures) to implement and

control some type of association (e.g., communication) between

systems. (E.g., see: Internet Protocol.)

and communication that are performed by two or more system

entities to achieve a joint objective. [A9042]

$ protocol suite

(I) A complementary collection of communication protocols used in

a computer network. (See: Internet, OSI.)

$ proxy server

(I) A computer process--often used as, or as part of, a firewall--

that relays a protocol between client and server computer systems,

by appearing to the client to be the server and appearing to the

server to be the client. (See: SOCKS.)

which may support proxies for several protocols (e.g., FTP, HTTP,

and TELNET). Instead of a client in the protected enclave

connecting directly to an external server, the internal client

connects to the proxy server which in turn connects to the

external server. The proxy server waits for a request from inside

the firewall, forwards the request to the remote server outside

the firewall, gets the response, then sends the response back to

the client. The proxy may be transparent to the clients, or they

may need to connect first to the proxy server, and then use that

association to also initiate a connection to the real server.

to perform caching, high-level logging, and access control. A

proxy can provide security service beyond that which is normally

part of the relayed protocol, such as access control based on peer

entity authentication of clients, or peer entity authentication of

servers when clients do not have that capability. A proxy at OSI

layer 7 can also provide finer-grained security service than can a

filtering router at OSI layer 3. For example, an FTP proxy could

permit transfers out of, but not into, a protected network.

$ pseudo-random

(I) A sequence of values that appears to be random (i.e.,

unpredictable) but is actually generated by a deterministic

algorithm. (See: random.)

$ pseudo-random number generator

(I) A process used to deterministically generate a series of

numbers (usually integers) that appear to be random according to

certain statistical tests, but actually are pseudo-random.

software.

$ public component

(I) A synonym for "public key".

(D) In most cases, ISDs SHOULD NOT use this term; to avoid

confusing readers, use "private key" instead. However, the term

MAY be used when specifically discussing a key pair; e.g., "A key

pair has a public component and a private component."

$ public key

(I) The publicly-disclosable component of a pair of cryptographic

keys used for asymmetric cryptography. (See: key pair, private

key.)

(O) "(In a public key cryptosystem) that key of a user's key pair

which is publicly known." [X509]

$ public-key certificate

(I) A digital certificate that binds a system entity's identity to

a public key value, and possibly to additional data items; a

digitally-signed data structure that attests to the ownership of a

public key. (See: X.509 public-key certificate.)

unforgeable. Thus, the certificate can be published, such as by

posting it in a directory, without the directory having to protect

the certificate's data integrity.

(O) "The public key of a user, together with some other

information, rendered unforgeable by encipherment with the private

key of the certification authority which issued it." [X509]

$ public-key cryptography

(I) The popular synonym for "asymmetric cryptography".

$ Public-Key Cryptography Standards (PKCS)

(I) A series of specifications published by RSA Laboratories for

data structures and algorithm usage for basic applications of

asymmetric cryptography. (See: PKCS #7, PKCS #10, PKCS #11.)

academia, originally including Apple, Digital, Lotus, Microsoft,

Northern Telecom, Sun, and MIT. Today, the specifications are

widely used, but they are not sanctioned by an official standards

organization, such as ANSI, ITU-T, or IETF. RSA Laboratories

retains sole decision-making authority over the PKCS.

$ public-key forward secrecy (PFS)

(I) For a key agreement protocol based on asymmetric cryptography,

the property that ensures that a session key derived from a set of

long-term public and private keys will not be compromised if one

of the private keys is compromised in the future.

either do not define it or do not define it precisely. While

preparing this Glossary, we tried to find a good definition for

that term, but found this to be a muddled area. Experts did not

agree. For all practical purposes, the literature defines "perfect

forward secrecy" by stating the Diffie-Hellman algorithm. The term

"public-key forward secrecy" (suggested by Hilarie Orman) and the

"I" definition stated for it here were crafted to be compatible

with current Internet documents, yet be narrow and leave room for

improved terminology.

taxonomy--a family of mutually exclusive and collectively

exhaustive terms and definitions to cover the basic properties

discussed here--for the full range of cryptographic algorithms and

protocols used in Internet Standards:

disagree about the basic ideas involved.

- One concept of "forward secrecy" is that, given observations of

the operation of a key establishment protocol up to time t, and

given some of the session keys derived from those protocol runs,

you cannot derive unknown past session keys or future session

keys.

- A related property is that, given observations of the protocol

and knowledge of the derived session keys, you cannot derive one

or more of the long-term private keys.

- The "I" definition presented above involves a third concept of

"forward secrecy" that refers to the effect of the compromise of

long-term keys.

- All three concepts involve the idea that a compromise of "this"

encryption key is not supposed to compromise the "next" one. There

also is the idea that compromise of a single key will compromise

only the data protected by the single key. In Internet literature,

the focus has been on protection against decryption of back

traffic in the event of a compromise of secret key material held

by one or both parties to a communication.

"forward", because compromise of "this" encryption key also is not

supposed to compromise the "previous" one, which is "backward"

rather than forward. In S/KEY, if the key used at time t is

compromised, then all keys used prior to that are compromised. If

the "long-term" key (i.e., the base of the hashing scheme) is

compromised, then all keys past and future are compromised; thus,

you could say that S/KEY has neither forward nor backward secrecy.

forward secrecy in the context of symmetric cryptographic systems.

In the absence of asymmetric cryptography, compromise of any long-

term key seems to compromise any session key derived from the

long-term key. For example, Kerberos isn't forward secret, because

compromising a client's password (thus compromising the key shared

by the client and the authentication server) compromises future

session keys shared by the client and the ticket-granting server.

disagree about the difference between these two. Some say there is

no difference, and some say that the initial naming was

unfortunate and suggest dropping the word "perfect". Some suggest

using "forward secrecy" for the case where one long-term private

key is compromised, and adding "perfect" for when both private

keys (or, when the protocol is multi-party, all private keys) are

compromised.

Van Oorschot, Michael Wiener, and, especially, Hilarie Orman

contributed ideas to this discussion.

$ public-key infrastructure (PKI)

(I) A system of CAs (and, optionally, RAs and other supporting

servers and agents) that perform some set of certificate

management, archive management, key management, and token

management functions for a community of users in an application of

asymmetric cryptography. (See: hierarchical PKI, mesh PKI,

security management infrastructure, trust-file PKI.)

(O) PKIX usage: The set of hardware, software, people, policies,

and procedures needed to create, manage, store, distribute, and

revoke digital certificates based on asymmetric cryptography.

their public-key certificates, (b) to revoke certificates when

required, and (c) to archive data needed to validate certificates

at a much later time. Key pairs for data confidentiality may be

generated (and perhaps escrowed) by CAs or RAs, but requiring a

PKI client to generate its own digital signature key pair helps

maintain system integrity of the cryptographic system, because

then only the client ever possesses the private key it uses. Also,

an authority may be established to approve or coordinate CPSs,

which are security policies under which components of a PKI

operate.

and PKI clients may obtain services from them. The full range of

such services is not yet fully understood and is evolving, but

supporting roles may include archive agent, certified delivery

agent, confirmation agent, digital notary, directory, key escrow

agent, key generation agent, naming agent who ensures that issuers

and subjects have unique identifiers within the PKI, repository,

ticket-granting agent, and time stamp agent.

$ RA

See: registration authority.

$ RA domains

(I) A capability of a CAW that allows a CA to divide the

responsibility for certification requests among multiple RAs.

authorization data that is provided with a certification request,

and to distribute the responsibility to review and approve

certification requests in high volume environments. RA domains

might segregate certification requests according to an attribute

of the certificate subject, such as an organizational unit.

$ RADIUS

See: Remote Authentication Dial-In User Service.

$ Rainbow Series

(O) A set of more than 30 technical and policy documents with

colored covers, issued by the NCSC, that discuss in detail the

TCSEC and provide guidance for meeting and applying the criteria.

(See: Green Book, Orange Book, Red Book, Yellow Book.)

$ random

(I) General usage: In mathematics, random means "unpredictable". A

sequence of values is called random if each successive value is

obtained merely by chance and does not depend on the preceding

values of the sequence, and a selected individual value is called

random if each of the values in the total population of

possibilities has equal probability of being selected. [Knuth]

(See: cryptographic key, pseudo-random, random number generator.)

(I) Security usage: In cryptography and other security

applications, random means not only unpredictable, but also

"unguessable". When selecting data values to use for cryptographic

keys, "the requirement is for data that an adversary has a very

low probability of guessing or determining." It is not sufficient

to use data that "only meets traditional statistical tests for

randomness or which is based on limited range sources, such as

clocks. Frequently such random quantities are determinable [i.e.,

guessable] by an adversary searching through an embarrassingly

small space of possibilities." [R1750]

$ random number generator

(I) A process used to generate an unpredictable, uniformly

distributed series of numbers (usually integers). (See: pseudo-

random, random.)

depend on the output of a "noisy diode" or other physical

phenomena. [R1750]

$ RBAC

See: Role-Based Access Control.

$ RC2

$ RC4

See: Rivest Cipher #2, Rivest Cipher #4.

$ realm

(O) Kerberos usage: The domain of authority of a Kerberos server

(consisting of an authentication server and a ticket-granting

server), including the Kerberized clients and the Kerberized

application servers

$ RED

(I) Designation for information system equipment or facilities

that handle (and for data that contains) only plaintext (or,

depending on the context, classified information), and for such

data itself. This term derives from U.S. Government COMSEC

terminology. (See: BLACK, RED/BLACK separation.)

$ Red Book

(D) ISDs SHOULD NOT use this term as a synonym for "Trusted

Network Interpretation of the Trusted Computer System Evaluation

Criteria" [NCS05]. Instead, use the full proper name of the

document or, in subsequent references, a more conventional

abbreviation. (See: TCSEC, Rainbow Series, (usage note under)

Green Book.)

$ RED/BLACK separation

(I) An architectural concept for cryptographic systems that

strictly separates the parts of a system that handle plaintext

(i.e., RED information) from the parts that handle ciphertext

(i.e., BLACK information). This term derives from U.S. Government

COMSEC terminology. (See: BLACK, RED.)

$ reference monitor

(I) "An access control concept that refers to an abstract machine

that mediates all accesses to objects by subjects." [NCS04] (See:

security kernel.)

every access), (b) isolated (i.e., it cannot be modified by other

system entities), and (c) verifiable (i.e., small enough to be

subjected to analysis and tests to ensure that it is correct).

$ reflection attack

(I) A type of replay attack in which transmitted data is sent back

to its originator.

$ register

$ registration

(I) An administrative act or process whereby an entity's name and

other attributes are established for the first time at a CA, prior

to the CA issuing a digital certificate that has the entity's name

as the subject. (See: registration authority.)

or indirectly, by a separate RA. An entity is presented to the CA

or RA, and the authority either records the name(s) claimed for

the entity or assigns the entity's name(s). The authority also

determines and records other attributes of the entity that are to

be bound in a certificate (such as a public key or authorizations)

or maintained in the authority's database (such as street address

and telephone number). The authority is responsible, possibly

assisted by an RA, for authenticating the entity's identity and

verifying the correctness of the other attributes, in accordance

with the CA's CPS.

following [R2527]:

- How a claimed identity and other attributes are verified.

- How organization affiliation or representation is verified.

- What forms of names are permitted, such as X.500 DN, domain

name, or IP address.

- Whether names are required to be meaningful or unique, and

within what domain.

- How naming disputes are resolved, including the role of

trademarks.

- Whether certificates are issued to entities that are not

persons.

- Whether a person is required to appear before the CA or RA, or

can instead be represented by an agent.

- Whether and how an entity proves possession of the private key

matching a public key.

$ registration authority (RA)

(I) An optional PKI entity (separate from the CAs) that does not

sign either digital certificates or CRLs but has responsibility

for recording or verifying some or all of the information

(particularly the identities of subjects) needed by a CA to issue

certificates and CRLs and to perform other certificate management

functions. (See: organizational registration authority,

registration.)

functions for all end users for which the CA signs certificates.

Other times, such as in a large or geographically dispersed

community, it may be necessary or desirable to offload secondary

CA functions and delegate them to an assistant, while the CA

retains the primary functions (signing certificates and CRLs). The

tasks that are delegated to an RA by a CA may include personal

authentication, name assignment, token distribution, revocation

reporting, key generation, and archiving. An RA is an optional PKI

component, separate from the CA, that is assigned secondary

functions. The duties assigned to RAs vary from case to case but

may include the following:

- Verifying a subject's identity, i.e., performing personal

authentication functions.

- Assigning a name to a subject. (See: distinguished name.)

- Verifying that a subject is entitled to have the attributes

requested for a certificate.

- Verifying that a subject possesses the private key that matches

the public key requested for a certificate.

- Performing functions beyond mere registration, such as

generating key pairs, distributing tokens, and handling

revocation reports. (Such functions may be assigned to a PKI

element that is separate from both the CA and the RA.)

(I) PKIX usage: An optional PKI component, separate from the

CA(s). The functions that the RA performs will vary from case to

case but may include identity authentication and name assignment,

key generation and archiving of key pairs, token distribution, and

revocation reporting. [R2510]

(O) SET usage: "An independent third-party organization that

processes payment card applications for multiple payment card

brands and forwards applications to the appropriate financial

institutions." [SET2]

$ regrade

(I) Deliberately change the classification level of information in

an authorized manner.

$ rekey

(I) Change the value of a cryptographic key that is being used in

an application of a cryptographic system. (See: certificate

rekey.)

key lifetime.

$ reliability

(I) The ability of a system to perform a required function under

stated conditions for a specified period of time. (See:

availability, survivability.)

$ relying party

(N) A synonym for "certificate user". Used in a legal context to

mean a recipient of a certificate who acts in reliance on that

certificate. (See: ABA Guidelines.)

$ Remote Authentication Dial-In User Service (RADIUS)

(I) An Internet protocol [R2138] for carrying dial-in users'

authentication information and configuration information between a

shared, centralized authentication server (the RADIUS server) and

a network access server (the RADIUS client) that needs to

authenticate the users of its network access ports. (See: TACACS.)

information to the client, and the client passes that information

to the RADIUS server. The server authenticates the client using a

shared secret value, then checks the user's authentication

information, and finally returns to the client all authorization

and configuration information needed by the client to deliver

service to the user.

$ renew

See: certificate renewal.

$ replay attack

(I) An attack in which a valid data transmission is maliciously or

fraudulently repeated, either by the originator or by an adversary

who intercepts the data and retransmits it, possibly as part of a

masquerade attack. (See: active wiretapping.)

$ repository

(I) A system for storing and distributing digital certificates and

related information (including CRLs, CPSs, and certificate

policies) to certificate users. (See: directory.)

(O) "A trustworthy system for storing and retrieving certificates

or other information relevant to certificates." [ABA]

putting it in a repository. The repository usually is a publicly

accessible, on-line server. In the Federal Public-key

Infrastructure, for example, the expected repository is a

directory that uses LDAP, but also may be the X.500 Directory that

uses DAP, or an HTTP server, or an FTP server that permits

anonymous login.

$ repudiation

(I) Denial by a system entity that was involved in an association

(especially an association that transfers information) of having

participated in the relationship. (See: accountability, non-

repudiation service.)

(O) "Denial by one of the entities involved in a communication of

having participated in all or part of the communication." [I7498

Part 2]

$ Request for Comment (RFC)

(I) One of the documents in the archival series that is the

official channel for ISDs and other publications of the Internet

Engineering Steering Group, the Internet Architecture Board, and

the Internet community in general. [R2026, R2223] (See: Internet

Standard.)

$ residual risk

(I) The risk that remains after countermeasures have been applied.

$ restore

See: card restore.

$ revocation

See: certificate revocation.

$ revocation date

(N) In an X.509 CRL entry, a date-time field that states when the

certificate revocation occurred, i.e., when the CA declared the

digital certificate to be invalid. (See: invalidity date.)

the worst case, all signatures made during the validity period of

the certificate may have to be considered invalid. However, it may

be desirable to treat a digital signature as valid even though the

private key used to sign was compromised after the signing. If

more is known about when the compromise actually occurred, a

second date-time, an "invalidity date", can be included in an

extension of the CRL entry.

$ revocation list

See: certificate revocation list.

$ revoke

See: certificate revocation.

$ RFC

See: Request for Comment.

$ risk

(I) An expectation of loss expressed as the probability that a

particular threat will exploit a particular vulnerability with a

particular harmful result.

(O) SET usage: "The possibility of loss because of one or more

threats to information (not to be confused with financial or

business risk)." [SET2]

$ risk analysis

$ risk assessment

(I) A process that systematically identifies valuable system

resources and threats to those resources, quantifies loss

exposures (i.e., loss potential) based on estimated frequencies

and costs of occurrence, and (optionally) recommends how to

allocate resources to countermeasures so as to minimize total

exposure.

thereby determining where countermeasures should be applied first.

It is usually financially and technically infeasible to counteract

all aspects of risk, and so some residual risk will remain, even

after all available countermeasures have been deployed. [FP031,

R2196]

$ risk management

(I) The process of identifying, controlling, and eliminating or

minimizing uncertain events that may affect system resources.

(See: risk analysis.)

$ Rivest Cipher #2 (RC2)

(N) A proprietary, variable-key-length block cipher invented by

Ron Rivest for RSA Data Security, Inc. (now a wholly-owned

subsidiary of Security Dynamics, Inc.).

$ Rivest Cipher #4 (RC4)

(N) A proprietary, variable-key-length stream cipher invented by

Ron Rivest for RSA Data Security, Inc. (now a wholly-owned

subsidiary of Security Dynamics, Inc.).

$ Rivest-Shamir-Adleman (RSA)

(N) An algorithm for asymmetric cryptography, invented in 1977 by

Ron Rivest, Adi Shamir, and Leonard Adleman [RSA78, Schn].

numbers. The difficulty of breaking RSA is believed to be

equivalent to the difficulty of factoring integers that are the

product of two large prime numbers of approximately equal size.

numbers, p and q, and compute the modulus, n = pq. Randomly choose

a number e, the public exponent, that is less than n and

relatively prime to (p-1)(q-1). Choose another number d, the

private exponent, such that ed-1 evenly divides (p-1)(q-1). The

public key is the set of numbers (n,e), and the private key is the

set (n,d).

from the public key (n,e). However, if n can be factored into p

and q, then the private key d can be computed easily. Thus, RSA

security depends on the assumption that it is computationally

difficult to factor a number that is the product of two large

prime numbers. (Of course, p and q are treated as part of the

private key, or else destroyed after computing n.)

Bob's public key (n,e) to compute m**e (mod n) = c. She sends c to

Bob. Bob computes c**d (mod n) = m. Only Bob knows d, so only Bob

can compute c**d (mod n) = m to recover m.

sent to Bob, Alice computes m**d (mod n) = s, where (d,n) is

Alice's private key. She sends m and s to Bob. To recover the

message that only Alice could have sent, Bob computes s**e (mod n)

= m, where (e,n) is Alice's public key.

authentication requires extra computation steps in which Alice and

Bob use a cryptographic hash function h (as explained for digital

signature). Alice computes the hash value h(m) = v, and then

encrypts v with her private key to get s. She sends m and s. Bob

receives m' and s', either of which might have been changed from

the m and s that Alice sent. To test this, he decrypts s' with

Alice's public key to get v'. He then computes h(m') = v". If v'

equals v", Bob is assured that m' is the same m that Alice sent.

$ role-based access control (RBAC)

(I) A form of identity-based access control where the system

entities that are identified and controlled are functional

positions in an organization or process.

$ root

(I) A CA that is directly trusted by an end entity. Acquiring the

value of a root CA's public key involves an out-of-band procedure.

(I) Hierarchical PKI usage: The CA that is the highest level (most

trusted) CA in a certification hierarchy; i.e., the authority upon

whose public key all certificate users base their trust. (See: top

CA.)

to one or more additional CAs that form the second highest level.

Each of these CAs may issue certificates to more CAs at the third

highest level, and so on. To initialize operation of a

hierarchical PKI, the root's initial public key is securely

distributed to all certificate users in a way that does not depend

on the PKI's certification relationships. The root's public key

may be distributed simply as a numerical value, but typically is

distributed in a self-signed certificate in which the root is the

subject. The root's certificate is signed by the root itself

because there is no higher authority in a certification hierarchy.

The root's certificate is then the first certificate in every

certification path.

(O) MISSI usage: A name previously used for a MISSI policy

creation authority, which is not a root as defined above for

general usage, but is a CA at the second level of the MISSI

hierarchy, immediately subordinate to a MISSI policy approving

authority.

(O) UNIX usage: A user account (also called "superuser") that has

all privileges (including all security-related privileges) and

thus can manage the system and its other user accounts.

$ root certificate

(I) A certificate for which the subject is a root.

(I) Hierarchical PKI usage: The self-signed public-key certificate

at the top of a certification hierarchy.

$ root key

(I) A public key for which the matching private key is held by a

root.

$ root registry

(O) MISSI usage: A name previously used for a MISSI policy

approving authority.

$ router

(I) A computer that is a gateway between two networks at OSI layer

3 and that relays and directs data packets through that

internetwork. The most common form of router operates on IP

packets. (See: bridge.)

(I) Internet usage: In the context of the Internet protocol suite,

a networked computer that forwards Internet Protocol packets that

are not addressed to the computer itself. (See: host.)

$ RSA

See: Rivest-Shamir-Adleman.

$ rule-based security policy

(I) "A security policy based on global rules imposed for all

users. These rules usually rely on comparison of the sensitivity

of the resource being accessed and the possession of corresponding

attributes of users, a group of users, or entities acting on

behalf of users." [I7498 Part 2] (See: identity-based security

policy.)

$ safety

(I) The property of a system being free from risk of causing harm

to system entities and outside entities.

$ SAID

See: security association identifier.

$ salt

(I) A random value that is concatenated with a password before

applying the one-way encryption function used to protect passwords

that are stored in the database of an access control system. (See:

initialization value.)

dictionary attack.

$ sanitize

(I) Delete sensitive data from a file, a device, or a system; or

modify data so as to be able to downgrade its classification

level.

$ SASL

See: Simple Authentication and Security Layer.

$ SCA

See: subordinate certification authority.

$ scavenging

See: (secondary definition under) threat consequence.

$ screening router

(I) A synonym for "filtering router".

$ SDE

See: Secure Data Exchange.

$ SDNS

See: Secure Data Network System.

$ seal

(O) To use cryptography to provide data integrity service for a

data object. (See: sign, wrap.)

(D) ISDs SHOULD NOT use this definition; instead, use language

that is more specific with regard to the mechanism(s) used, such

as "sign" when the mechanism is digital signature.

$ secret

(I) (1.) Adjective: The condition of information being protected

from being known by any system entities except those who are

intended to know it. (2.) Noun: An item of information that is

protected thusly.

passwords.

$ secret-key cryptography

(I) A synonym for "symmetric cryptography".

$ Secure Data Exchange (SDE)

(N) A local area network security protocol defined by the IEEE

802.10 standard.

$ Secure Data Network System (SDNS)

(N) An NSA program that developed security protocols for

electronic mail (Message Security Protocol), OSI layer 3 (SP3),

OSI layer 4 (SP4), and key management (KMP).

$ Secure Hash Standard (SHS)

(N) The U.S. Government standard [FP180] that specifies the Secure

Hash Algorithm (SHA-1), a cryptographic hash function that

produces a 160-bit output (hash result) for input data of any

length < 2**64 bits.

$ Secure Hypertext Transfer Protocol (Secure-HTTP, S-HTTP)

(I) A Internet protocol for providing client-server security

services for HTTP communications. (See: https.)

businesses interested in developing the Internet for commercial

uses. Several message formats may be incorporated into S-HTTP

clients and servers, particularly CMS and MOSS. S-HTTP supports

choice of security policies, key management mechanisms, and

cryptographic algorithms through option negotiation between

parties for each transaction. S-HTTP supports both asymmetric and

symmetric key operation modes. S-HTTP attempts to avoid presuming

a particular trust model, but it attempts to facilitate multiply-

rooted hierarchical trust and anticipates that principals may have

many public key certificates.

$ Secure/MIME (S/MIME)

(I) Secure/Multipurpose Internet Mail Extensions, an Internet

protocol [R2633] to provide encryption and digital signatures for

Internet mail messages.

$ Secure Sockets Layer (SSL)

(N) An Internet protocol (originally developed by Netscape

Communications, Inc.) that uses connection-oriented end-to-end

encryption to provide data confidentiality service and data

integrity service for traffic between a client (often a web

browser) and a server, and that can optionally provide peer entity

authentication between the client and the server. (See: Transport

Layer Security.)

protocol (TCP). SSL is independent of the application it

encapsulates, and any higher level protocol can layer on top of

SSL transparently. However, many Internet applications might be

better served by IPsec.

Protocol, is layered on top of the transport protocol and

encapsulates higher level protocols. One such encapsulated

protocol is SSL Handshake Protocol. (b) SSL's upper layer provides

asymmetric cryptography for server authentication (verifying the

server's identity to the client) and optional client

authentication (verifying the client's identity to the server),

and also enables them to negotiate a symmetric encryption

algorithm and secret session key (to use for data confidentiality)

before the application protocol transmits or receives data. A

keyed hash provides data integrity service for encapsulated data.

$ secure state

(I) A system condition in which no subject can access any object

in an unauthorized manner. (See: (secondary definition under)

Bell-LaPadula Model, clean system.)

$ security

(I) (1.) Measures taken to protect a system. (2.) The condition of

a system that results from the establishment and maintenance of

measures to protect the system. (3.) The condition of system

resources being free from unauthorized access and from

unauthorized or accidental change, destruction, or loss.

$ security architecture

(I) A plan and set of principles that describe (a) the security

services that a system is required to provide to meet the needs of

its users, (b) the system elements required to implement the

services, and (c) the performance levels required in the elements

to deal with the threat environment. (See: (discussion under)

security policy.)

engineering process. A complete system security architecture

includes administrative security, communication security, computer

security, emanations security, personnel security, and physical

security (e.g., see: [R2179]). A complete security architecture

needs to deal with both intentional, intelligent threats and

accidental kinds of threats.

$ security association

(I) A relationship established between two or more entities to

enable them to protect data they exchange. The relationship is

used to negotiate characteristics of protection mechanisms, but

does not include the mechanisms themselves. (See: association.)

security services. The relationship is represented by a set of

information that is shared between the entities and is agreed upon

and considered a contract between them.

(O) IPsec usage: A simplex (uni-directional) logical connection

created for security purposes and implemented with either AH or

ESP (but not both). The security services offered by a security

association depend on the protocol selected, the IPsec mode

(transport or tunnel), the endpoints, and the election of optional

services within the protocol. A security association is identified

by a triple consisting of (a) a destination IP address, (b) a

protocol (AH or ESP) identifier, and (c) a Security Parameter

Index.

$ security association identifier (SAID)

(I) A data field in a security protocol (such as NLSP or SDE),

used to identify the security association to which a protocol data

unit is bound. The SAID value is usually used to select a key for

decryption or authentication at the destination. (See: Security

Parameter Index.)

$ security audit

(I) An independent review and examination of a system's records

and activities to determine the adequacy of system controls,

ensure compliance with established security policy and procedures,

detect breaches in security services, and recommend any changes

that are indicated for countermeasures. [I7498 Part 2, NCS01]

system entities that initiate or participate in security-relevant

events and actions. Thus, means are needed to generate and record

a security audit trail and to review and analyze the audit trail

to discover and investigate attacks and security compromises.

$ security audit trail

(I) A chronological record of system activities that is sufficient

to enable the reconstruction and examination of the sequence of

environments and activities surrounding or leading to an

operation, procedure, or event in a security-relevant transaction

from inception to final results. [NCS04] (See: security audit.)

$ security class

(D) A synonym for "security level". For consistency, ISDs SHOULD

use "security level" instead of "security class".

$ security clearance

(I) A determination that a person is eligible, under the standards

of a specific security policy, for authorization to access

sensitive information or other system resources. (See: clearance

level.)

$ security compromise

(I) A security violation in which a system resource is exposed, or

is potentially exposed, to unauthorized access. (See: data

compromise, violation.)

$ security domain

See: domain.

$ security environment

(I) The set of external entities, procedures, and conditions that

affect secure development, operation, and maintenance of a system.

$ security event

(I) A occurrence in a system that is relevant to the security of

the system. (See: security incident.)

those that are not. In a CA workstation, for example, a list of

security events might include the following:

- Performing a cryptographic operation, e.g., signing a digital

certificate or CRL.

- Performing a cryptographic card operation: creation, insertion,

removal, or backup.

- Performing a digital certificate lifecycle operation: rekey,

renewal, revocation, or update.

- Posting information to an X.500 Directory.

- Receiving a key compromise notification.

- Receiving an improper certification request.

- Detecting an alarm condition reported by a cryptographic

module.

- Logging the operator in or out.

- Failing a built-in hardware self-test or a software system

integrity check.

$ security fault analysis

(I) A security analysis, usually performed on hardware at a logic

gate level, gate-by-gate, to determine the security properties of

a device when a hardware fault is encountered.

$ security gateway

(I) A gateway that separates trusted (or relatively more trusted)

hosts on the internal network side from untrusted (or less

trusted) hosts on the external network side. (See: firewall and

guard.)

(O) IPsec usage: "An intermediate system that implements IPsec

protocols." [R2401] Normally, AH or ESP is implemented to serve a

set of internal hosts, providing security services for the hosts

when they communicate with other, external hosts or gateways that

also implement IPsec.

$ security incident

(I) A security event that involves a security violation. (See:

CERT, GRIP, security event, security intrusion, security

violation.)

system's security policy is disobeyed or otherwise breached.

(O) "Any adverse event which compromises some aspect of computer

or network security." [R2350]

(D) ISDs SHOULD NOT use this "O" definition because (a) a security

incident may occur without actually being harmful (i.e., adverse)

and (b) this Glossary defines "compromise" more narrowly in

relation to unauthorized access.

$ security intrusion

(I) A security event, or a combination of multiple security

events, that constitutes a security incident in which an intruder

gains, or attempts to gain, access to a system (or system

resource) without having authorization to do so.

$ security kernel

(I) "The hardware, firmware, and software elements of a trusted

computing base that implement the reference monitor concept. It

must mediate all accesses, be protected from modification, and be

verifiable as correct." [NCS04] (See: reference monitor.)

monitor for a given hardware base.

$ security label

(I) A marking that is bound to a system resource and that names or

designates the security-relevant attributes of that resource.

[I7498 Part 2, R1457]

term is understood more narrowly as a marking that represents the

security level of an information object, i.e., a marking that

indicates how sensitive an information object is. [NCS04]

to applicable security policy to determine how to control access

to the associated information, otherwise constrain its handling,

and affix appropriate security markings to visible (printed and

displayed) images thereof. [FP188]

$ security level

(I) The combination of a hierarchical classification level and a

set of non-hierarchical category designations that represents how

sensitive information is. (See: (usage note under) classification

level, dominate, lattice model.)

$ security management infrastructure (SMI)

(I) System elements and activities that support security policy by

monitoring and controlling security services and mechanisms,

distributing security information, and reporting security events.

The associated functions are as follows [I7498-4]:

- Controlling (granting or restricting) access to system

resources: This includes verifying authorizations and

identities, controlling access to sensitive security data, and

modifying access priorities and procedures in the event of

attacks.

- Retrieving (gathering) and archiving (storing) security

information: This includes logging security events and

analyzing the log, monitoring and profiling usage, and

reporting security violations.

- Managing and controlling the encryption process: This includes

performing the functions of key management and reporting on key

management problems. (See: public-key infrastructure.)

$ security mechanism

(I) A process (or a device incorporating such a process) that can

be used in a system to implement a security service that is

provided by or within the system. (See: (discussion under)

security policy.)

exchange, checksum, digital signature, encryption, and traffic

padding.

$ security model

(I) A schematic description of a set of entities and relationships

by which a specified set of security services are provided by or

within a system. (See: (discussion under) security policy.)

$ security parameters index (SPI)

(I) IPsec usage: The type of security association identifier used

in IPsec protocols. A 32-bit value used to distinguish among

different security associations terminating at the same

destination (IP address) and using the same IPsec security

protocol (AH or ESP). Carried in AH and ESP to enable the

receiving system to determine under which security association to

process a received packet.

$ security perimeter

(I) The boundary of the domain in which a security policy or

security architecture applies; i.e., the boundary of the space in

which security services protect system resources.

$ security policy

(I) A set of rules and practices that specify or regulate how a

system or organization provides security services to protect

sensitive and critical system resources. (See: identity-based

security policy, rule-based security policy, security

architecture, security mechanism, security model.)

(O) "The set of rules laid down by the security authority

governing the use and provision of security services and

facilities." [X509]

of the security engineering process (as shown in the following

diagram). Each layer provides a different view of security,

ranging from what services are needed to how services are

implemented.

What Security Services Should Be Provided?

+ - - - - - - - - - - - +

Security Policy

+ - - - - - - - - - - - + + - - - - - - - - - - - - - - +

Security Model A "top-level specification"

+ - - - - - - - - - - - + <- is at a level below "model"

Security Architecture but above "architecture".

+ - - - - - - - - - - - + + - - - - - - - - - - - - - - +

Security Mechanism

+ - - - - - - - - - - - +

How Are Security Services Implemented?

$ Security Protocol 3 (SP3)

(O) A protocol [SDNS3] developed by SDNS to provide connectionless

data security at the top of OSI layer 3. (See: NLSP.)

$ Security Protocol 4 (SP4)

(O) A protocol [SDNS4] developed by SDNS to provide either

connectionless or end-to-end connection-oriented data security at

the bottom of OSI layer 4. (See: TLSP.)

$ security-relevant event

See: security event.

$ security service

(I) A processing or communication service that is provided by a

system to give a specific kind of protection to system resources.

(See: access control service, audit service, availability service,

data confidentiality service, data integrity service, data origin

authentication service, non-repudiation service, peer entity

authentication service, system integrity service.)

(O) "A service, provided by a layer of communicating open systems,

which ensures adequate security of the systems or the data

transfers." [I7498 Part 2]

implemented by security mechanisms.

$ security situation

(I) ISAKMP usage: The set of all security-relevant information--

e.g., network addresses, security classifications, manner of

operation (normal or emergency)--that is needed to decide the

security services that are required to protect the association

that is being negotiated.

$ security token

See: token.

$ security violation

(I) An act or event that disobeys or otherwise breaches security

policy. (See: compromise, penetration, security incident.)

$ self-signed certificate

(I) A public-key certificate for which the public key bound by the

certificate and the private key used to sign the certificate are

components of the same key pair, which belongs to the signer.

(See: root certificate.)

is the same as the subject's DN.

$ semantic security

(I) An attribute of a encryption algorithm that is a formalization

of the notion that the algorithm not only hides the plaintext but

also reveals no partial information about the plaintext. Whatever

is efficiently computable about the plaintext when given the

ciphertext, is also efficiently computable without the ciphertext.

(See: indistinguishability.)

$ sensitive (information)

(I) Information is sensitive if disclosure, alteration,

destruction, or loss of the information would adversely affect the

interests or business of its owner or user. (See: critical.)

$ separation of duties

(I) The practice of dividing the steps in a system function among

different individuals, so as to keep a single individual from

subverting the process. (See: dual control, administrative

security.)

$ serial number

See: certificate serial number.

$ server

(I) A system entity that provides a service in response to

requests from other system entities called clients.

$ session key

(I) In the context of symmetric encryption, a key that is

temporary or is used for a relatively short period of time. (See:

ephemeral key, key distribution center, master key.)

communication between two computers, such as for the duration of a

single connection or transaction set, or the key is used in an

application that protects relatively large amounts of data and,

therefore, needs to be rekeyed frequently.

$ SET

See: SET Secure Electronic Transaction(trademark).

$ SET private extension

(O) One of the private extensions defined by SET for X.509

certificates. Carries information about hashed root key,

certificate type, merchant data, cardholder certificate

requirements, encryption support for tunneling, or message support

for payment instructions.

$ SET qualifier

(O) A certificate policy qualifier that provides information about

the location and content of a SET certificate policy.

own certificate, each CA in the SET certification hierarchy may

add one qualifying statement to the root policy when the CA issues

a certificate. The additional qualifier is a certificate policy

for that CA. Each policy in a SET certificate may have these

qualifiers:

- A URL where a copy of the policy statement may be found.

- An electronic mail address where a copy of the policy statement

may be found.

- A hash result of the policy statement, computed using the

indicated algorithm.

- A statement declaring any disclaimers associated with the

issuing of the certificate.

$ SET Secure Electronic Transaction(trademark) or SET(trademark)

(N) A protocol developed jointly by MasterCard International and

Visa International and published as an open standard to provide

confidentiality of transaction information, payment integrity, and

authentication of transaction participants for payment card

transactions over unsecured networks, such as the Internet. [SET1]

(See: acquirer, brand, cardholder, dual signature, electronic

commerce, issuer, merchant, payment gateway, third party.)

Visa announced the SET standard on 1 February 1996. On 19 December

1997, MasterCard and Visa formed SET Secure Electronic Transaction

LLC (commonly referred to as "SETCo") to implement the SET 1.0

specification. A memorandum of understanding adds American Express

and JCB Credit Card Company as co-owners of SETCo.

$ SETCo

See: (secondary definition under) SET Secure Electronic

Transaction.

$ SHA-1

See: Secure Hash Standard.

$ shared secret

(I) A synonym for "keying material" or "cryptographic key".

$ S-HTTP

See: Secure HTTP.

$ sign

(I) Create a digital signature for a data object.

$ signature

See: digital signature, electronic signature.

$ signature certificate

(I) A public-key certificate that contains a public key that is

intended to be used for verifying digital signatures, rather than

for encrypting data or performing other cryptographic functions.

extension which indicates the purpose for which the certified

public key is intended.

$ signer

(N) A human being or an organization entity that uses its private

key to create a digital signature for a data object. [ABA]

$ SILS

See: Standards for Interoperable LAN/MAN Security.

$ simple authentication

(I) An authentication process that uses a password as the

information needed to verify an identity claimed for an entity.

(See: strong authentication.)

(O) "Authentication by means of simple password arrangements."

[X509]

$ Simple Authentication and Security Layer (SASL)

(I) An Internet specification [R2222] for adding authentication

service to connection-based protocols. To use SASL, a protocol

includes a command for authenticating a user to a server and for

optionally negotiating protection of subsequent protocol

interactions. The command names a registered security mechanism.

SASL mechanisms include Kerberos, GSSAPI, S/KEY, and others. Some

protocols that use SASL are IMAP4 and POP3.

$ Simple Key-management for Internet Protocols (SKIP)

(I) A key distribution protocol that uses hybrid encryption to

convey session keys that are used to encrypt data in IP packets.

[R2356] (See: IKE, IPsec.)

key agreement algorithm) to generate a key-encrypting key for use

between two entities. A session key is used with a symmetric

algorithm to encrypt data in one or more IP packets that are to be

sent from one of the entities to the other. The KEK is used with a

symmetric algorithm to encrypt the session key, and the encrypted

session key is placed in a SKIP header that is added to each IP

packet that is encrypted with that session key.

$ Simple Mail Transfer Protocol (SMTP)

(I) A TCP-based, application-layer, Internet Standard protocol

[R0821] for moving electronic mail messages from one computer to

another.

$ Simple Network Management Protocol (SNMP)

(I) A UDP-based, application-layer, Internet Standard protocol

[R2570, R2574] for conveying management information between

managers and agents.

access control. (See: community string.) Version 2 adds

cryptographic mechanisms based on DES and MD5. Version 3 provides

enhanced, integrated support for security services, including data

confidentiality, data integrity, data origin authentication, and

message timeliness and limited replay protection.

$ simple security property

See: (secondary definition under) Bell-LaPadula Model.

$ single sign-on

(I) A system that enables a user to access multiple computer

platforms (usually a set of hosts on the same network) or

application systems after being authenticated just one time. (See:

Kerberos.)

granted access to a variety of permitted resources with no further

has the advantages of being user friendly and enabling

authentication to be managed consistently across an entire

enterprise, and has the disadvantage of requiring all hosts and

applications to trust the same authentication mechanism.

$ situation

See: security situation.

$ S/Key

(I) A security mechanism that uses a cryptographic hash function

to generate a sequence of 64-bit, one-time passwords for remote

user login. [R1760]

cryptographic hash function multiple times to the user's secret

key. For each successive authentication of the user, the number of

hash applications is reduced by one. (Thus, an intruder using

wiretapping cannot compute a valid password from knowledge of one

previously used.) The server verifies a password by hashing the

currently presented password (or initialization value) one time

and comparing the hash result with the previously presented

password.

$ SKIP

See: Simple Key-management for IP.

$ SKIPJACK

(N) A Type II block cipher [NIST] with a block size of 64 bits and

a key size of 80 bits, that was developed by NSA and formerly

classified at the U.S. Department of Defense "Secret" level. (See:

CAPSTONE, CLIPPER, FORTEZZA, Key Exchange Algorithm.)

declassified.

$ slot

(O) MISSI usage: One of the FORTEZZA PC card storage areas that

are each able to hold an X.509 certificate and additional data

that is associated with the certificate, such as the matching

private key.

$ smart card

(I) A credit-card sized device containing one or more integrated

circuit chips, which perform the functions of a computer's central

processor, memory, and input/output interface. (See: PC card.)

that closely conforms to the dimensions and appearance of the kind

of plastic credit card issued by banks and merchants. At other

times, the term is used loosely to include cards that are larger

than credit cards, especially cards that are thicker, such as PC

cards.

smart card except that rather than having standard credit card

dimensions, the token is packaged in some other form, such as a

dog tag or door key shape.

$ smart token

See: (secondary definition under) smart card.

$ SMI

See: security management infrastructure.

$ S/MIME

See: Secure/MIME.

$ SMTP

See: Simple Mail Transfer Protocol.

$ smurf

(I) Software that mounts a denial-of-service attack ("smurfing")

by exploiting IP broadcast addressing and ICMP ping packets to

cause flooding. (See: flood, ICMP flood.)

(D) ISDs SHOULD NOT use this term because it is not listed in most

dictionaries and could confuse international readers.

originate from another address, that of the "victim", either a

host or an IP router. The packet contains an ICMP ping message

that is addressed to an IP broadcast address, i.e., to all IP

addresses in a given network. The echo responses to the ping

message return to the victim's address. The goal of smurfing may

be either to deny service at a particular host or to flood all or

part of an IP network.

$ sniffing

(D) ISDs SHOULD NOT use this term because it unnecessarily

duplicates the meaning of a term that is better established. (See:

(usage note under) Green Book.

$ SNMP

See: Simple Network Management Protocol.

$ social engineering

(I) A euphemism for non-technical or low-technology means--such as

lies, impersonation, tricks, bribes, blackmail, and threats--used

to attack information systems. (See: masquerade attack.)

(D) ISDs SHOULD NOT use this term because it is vague; instead,

use a term that is specific with regard to the means of attack.

$ SOCKS

(I) An Internet protocol [R1928] that provides a generalized proxy

server that enables client-server applications--such as TELNET,

FTP, and HTTP; running over either TCP or UDP--to use the services

of a firewall.

transport layer. When a client inside a firewall wishes to

establish a connection to an object that is reachable only through

the firewall, it uses TCP to connect to the SOCKS server,

negotiates with the server for the authentication method to be

used, authenticates with the chosen method, and then sends a relay

request. The SOCKS server evaluates the request, typically based

on source and destination addresses, and either establishes the

appropriate connection or denies it.

$ soft TEMPEST

(O) The use of software techniques to reduce the radio frequency

information leakage from computer displays and keyboards. [Kuhn]

(See: TEMPEST.)

$ software

(I) Computer programs (which are stored in and executed by

computer hardware) and associated data (which also is stored in

the hardware) that may be dynamically written or modified during

execution. (See: firmware, hardware.)

$ SORA

See: SSO-PIN ORA.

$ source authentication

(D) ISDs SHOULD NOT use this term because it is ambiguous. If the

intent is to authenticate the original creator or packager of data

received, then say "data origin authentication". If the intent is

to authenticate the identity of the sender of data, then say "peer

entity authentication". (See: data origin authentication, peer

entity authentication).

$ source integrity

(I) The degree of confidence that can be placed in information

based on the trustworthiness of its sources. (See: integrity.)

$ SP3

See: Security Protocol 3.

$ SP4

See: Security Protocol 4.

$ spam

(I) (1.) Verb: To indiscriminately send unsolicited, unwanted,

irrelevant, or inappropriate messages, especially commercial

advertising in mass quantities. (2.) Noun: electronic "junk mail".

[R2635]

(D) This term SHOULD NOT be written in upper-case letters, because

SPAM(trademark) is a trademark of Hormel Foods Corporation. Hormel

says, "We do not object to use of this slang term [spam] to

describe [unsolicited commercial email (UCE)], although we do

object to the use of our product image in association with that

term. Also, if the term is to be used, it should be used in all

lower-case letters to distinguish it from our trademark SPAM,

which should be used with all uppercase letters."

flooding.) According to the SPAM Web site, the term was adopted as

a result of the Monty Python skit in which a group of Vikings sang

a chorus of 'SPAM, SPAM, SPAM . . .' in an increasing crescendo,

drowning out other conversation. Hence, the analogy applied

because UCE was drowning out normal discourse on the Internet.

$ SPC

See: software publisher certificate.

$ SPI

See: Security Parameters Index.

$ split key

(I) A cryptographic key that is divided into two or more separate

data items that individually convey no knowledge of the whole key

that results from combining the items. (See: dual control, split

knowledge.)

$ split knowledge

(I) A security technique in which two or more entities separately

hold data items that individually convey no knowledge of the

information that results from combining the items. (See: dual

control, split key.)

(O) "A condition under which two or more entities separately have

key components which individually convey no knowledge of the

plaintext key which will be produced when the key components are

combined in the cryptographic module." [FP140]

$ spoofing attack

(I) A synonym for "masquerade attack".

$ SSH

(I) A protocol for secure remote login and other secure network

services over an insecure network.

- Transport layer protocol: Provides server authentication,

confidentiality, and integrity. It may optionally also provide

compression. The transport layer will typically be run over a

TCP/IP connection, but might also be used on top of any other

reliable data stream.

- User authentication protocol: Authenticates the client-side

user to the server. It runs over the transport layer protocol.

- Connection protocol: Multiplexes the encrypted tunnel into

several logical channels. It runs over the user authentication

protocol.

$ SSL

See: Secure Sockets Layer, Standard Security Label.

$ SSO

See: system security officer.

$ SSO PIN

(O) MISSI usage: One of two personal identification numbers that

control access to the functions and stored data of a FORTEZZA PC

card. Knowledge of the SSO PIN enables the card user to perform

the FORTEZZA functions intended for use by an end user and also

the functions intended for use by a MISSI certification authority.

(See: user PIN.)

$ SSO-PIN ORA (SORA)

(O) MISSI usage: A MISSI organizational RA that operates in a mode

in which the ORA performs all card management functions and,

therefore, requires knowledge of the SSO PIN for an end user's

FORTEZZA PC card.

$ Standards for Interoperable LAN/MAN Security (SILS)

(N) (1.) The IEEE 802.10 standards committee. (2.) A developing

set of IEEE standards, which has eight parts: (a) Model, including

security management, (b) Secure Data Exchange protocol, (c) Key

Management, (d) [has been incorporated in (a)], (e) SDE Over

Ethernet 2.0, (f) SDE Sublayer Management, (g) SDE Security

Labels, and (h) SDE PICS Conformance. Parts b, e, f, g, and h are

incorporated in IEEE Standard 802.10-1998.

$ star property

(I) (Written "*-property".) See: "confinement property" under

Bell-LaPadula Model.

$ Star Trek attack

gone before.

$ steganography

(I) Methods of hiding the existence of a message or other data.

This is different than cryptography, which hides the meaning of a

message but does not hide the message itself. (See: cryptology.)

(See: digital watermark.)

$ storage channel

See: (secondary definition under) covert channel.

$ stream cipher

(I) An encryption algorithm that breaks plaintext into a stream of

successive bits (or characters) and encrypts the n-th plaintext

bit with the n-th element of a parallel key stream, thus

converting the plaintext bit stream into a ciphertext bit stream.

[Schn] (See: block cipher.)

$ strong authentication

(I) An authentication process that uses cryptography--particularly

public-key certificates--to verify the identity claimed for an

entity. (See: X.509.)

(O) "Authentication by means of cryptographically derived

credentials." [X509]

$ subject

1. (I) In a computer system: A system entity that causes

information to flow among objects or changes the system state;

technically, a process-domain pair. (See: Bell-LaPadula Model.)

2. (I) Of a certificate: The entity name that is bound to the data

items in a digital certificate, and particularly a name that is

bound to a key value in a public-key certificate.

$ subnetwork

(N) An OSI term for a system of packet relays and connecting links

that implement the lower three protocol layers of the OSIRM to

provide a communication service that interconnects attached end

systems. Usually the relays operate at OSI layer 3 and are all of

the same type (e.g., all X.25 packet switches, or all interface

units in an IEEE 802.3 LAN). (See: gateway, internet, router.)

$ subordinate certification authority (SCA)

(I) A CA whose public-key certificate is issued by another

(superior) CA. (See: certification hierarchy.)

(O) MISSI usage: The fourth-highest (bottom) level of a MISSI

certification hierarchy; a MISSI CA whose public-key certificate

is signed by a MISSI CA rather than by a MISSI PCA. A MISSI SCA is

the administrative authority for a subunit of an organization,

established when it is desirable to organizationally distribute or

decentralize the CA service. The term refers both to that

authoritative office or role, and to the person who fills that

office. A MISSI SCA registers end users and issues their

certificates and may also register ORAs, but may not register

other CAs. An SCA periodically issues a CRL.

$ subordinate distinguished name

(I) An X.500 DN is subordinate to another X.500 DN if it begins

with a set of attributes that is the same as the entire second DN

except for the terminal attribute of the second DN (which is

usually the name of a CA). For example, the DN <C=FooLand, O=Gov,

OU=Treasurer, CN=DukePinchpenny> is subordinate to the DN

<C=FooLand, O=Gov, CN=KingFooCA>.

$ superencryption

(I) An encryption operation for which the plaintext input to be

transformed is the ciphertext output of a previous encryption

operation.

$ survivability

(I) The ability of a system to remain in operation or existence

despite adverse conditions, including both natural occurrences,

accidental actions, and attacks on the system. (See: availability,

reliability.)

$ symmetric cryptography

(I) A branch of cryptography involving algorithms that use the

same key for two different steps of the algorithm (such as

encryption and decryption, or signature creation and signature

verification). (See: asymmetric cryptography.)

[Kahn]. A modern example of a symmetric encryption algorithm is

the U.S. Government's Data Encryption Algorithm. (See: DEA, DES.)

cryptography" (versus public-key cryptography) because the

entities that share the key, such as the originator and the

recipient of a message, need to keep the key secret. For example,

when Alice wants to ensure confidentiality for data she sends to

Bob, she encrypts the data with a secret key, and Bob uses the

same key to decrypt. Keeping the shared key secret entails both

cost and risk when the key is distributed to both Alice and Bob.

Thus, symmetric cryptography has a key management disadvantage

compared to asymmetric cryptography.

$ symmetric key

(I) A cryptographic key that is used in a symmetric cryptographic

algorithm.

$ SYN flood

(I) A denial of service attack that sends a host more TCP SYN

packets (request to synchronize sequence numbers, used when

opening a connection) than the protocol implementation can handle.

(See: flooding.)

$ system

for "automated information system".

$ system entity

(I) An active element of a system--e.g., an automated process, a

subsystem, a person or group of persons--that incorporates a

specific set of capabilities.

$ system high

(I) The highest security level supported by a system at a

particular time or in a particular environment. (See: system high

security mode.)

$ system high security mode

(I) A mode of operation of an information system, wherein all

users having access to the system possess a security clearance or

authorization, but not necessarily a need-to-know, for all data

handled by the system. (See: mode of operation.)

policy regarding system accreditation [DOD2], but the term is

widely used outside the Defense Department and outside the

Government.

$ system integrity

(I) "The quality that a system has when it can perform its

intended function in a unimpaired manner, free from deliberate or

inadvertent unauthorized manipulation." [NCS04] (See: system

integrity service.)

$ system integrity service

(I) A security service that protects system resources in a

verifiable manner against unauthorized or accidental change, loss,

or destruction. (See: system integrity.)

$ system low

(I) The lowest security level supported by a system at a

particular time or in a particular environment. (See: system

high.)

$ system resource

(I) Data contained in an information system; or a service provided

by a system; or a system capability, such as processing power or

communication bandwidth; or an item of system equipment (i.e., a

system component--hardware, firmware, software, or documentation);

or a facility that houses system operations and equipment.

$ system security officer (SSO)

(I) A person responsible for enforcement or administration of the

security policy that applies to the system.

$ system verification

See: (secondary definition under) verification.

$ TACACS

$ TACACS+

See: Terminal Access Controller (TAC) Access Control System.

$ tamper

(I) Make an unauthorized modification in a system that alters the

system's functioning in a way that degrades the security services

that the system was intended to provide.

$ TCB

See: trusted computing base.

$ TCP

See: Transmission Control Protocol.

$ TCP/IP

(I) A synonym for "Internet Protocol Suite", in which the

Transmission Control Protocol (TCP) and the Internet Protocol (IP)

are important parts.

$ TCSEC

See: Trusted Computer System Evaluation Criteria.

$ TELNET

(I) A TCP-based, application-layer, Internet Standard protocol

[R0854] for remote login from one host to another.

$ TEMPEST

(O) A nickname for specifications and standards for limiting the

strength of electromagnetic emanations from electrical and

electronic equipment and thus reducing vulnerability to

eavesdropping. This term originated in the U.S. Department of

Defense. [Army, Kuhn, Russ] (See: emanation security, soft

tempest.)

(D) ISDs SHOULD NOT use this term as a synonym for

"electromagnetic emanations security".

$ Terminal Access Controller (TAC) Access Control System (TACACS)

(I) A UDP-based authentication and access control protocol [R1492]

in which a network access server receives an identifier and

password from a remote terminal and passes them to a separate

authentication server for verification.

commercial equipment. TACs were a type of network access server

computer used to connect terminals to the early Internet, usually

using dial-up modem connections. TACACS used centralized

authentication servers and served not only network access servers

like TACs but also routers and other networked computing devices.

TACs are no longer in use, but TACACS+ is. [R1983]

- "XTACACS": The name of Cisco Corporation's implementation,

which enhances and extends the original TACACS.

- "TACACS+": A TCP-based protocol that improves on TACACS and

XTACACS by separating the functions of authentication,

authorization, and accounting and by encrypting all traffic

between the network access server and authentication server. It

is extensible to allow any authentication mechanism to be used

with TACACS+ clients.

$ TESS

See: The Exponential Encryption System.

$ The Exponential Encryption System (TESS)

(I) A system of separate but cooperating cryptographic mechanisms

and functions for the secure authenticated exchange of

cryptographic keys, the generation of digital signatures, and the

distribution of public keys. TESS employs asymmetric cryptography,

based on discrete exponentiation, and a structure of self-

certified public keys. [R1824]

$ threat

(I) A potential for violation of security, which exists when there

is a circumstance, capability, action, or event that could breach

security and cause harm. (See: attack, threat action, threat

consequence.)

vulnerability. A threat can be either "intentional" (i.e.,

intelligent; e.g., an individual cracker or a criminal

organization) or "accidental" (e.g., the possibility of a computer

malfunctioning, or the possibility of an "act of God" such as an

earthquake, a fire, or a tornado).

narrowly to refer only to intelligent threats:

(N) U. S. Government usage: The technical and operational

capability of a hostile entity to detect, exploit, or subvert

friendly information systems and the demonstrated, presumed, or

inferred intent of that entity to conduct such activity.

$ threat action

(I) An assault on system security. (See: attack, threat, threat

consequence.)

acts (i.e. attacks) and accidental events [FIPS31]. Various kinds

of threat actions are defined as subentries under "threat

consequence".

$ threat analysis

(I) An analysis of the probability of occurrences and consequences

of damaging actions to a system.

$ threat consequence

(I) A security violation that results from a threat action.

Includes disclosure, deception, disruption, and usurpation. (See:

attack, threat, threat action.)

consequences, and also list and describe the kinds of threat

actions that cause each consequence. Threat actions that are

accidental events are marked by "*".

1. "(Unauthorized) Disclosure" (a threat consequence): A

circumstance or event whereby an entity gains access to data

for which the entity is not authorized. (See: data

confidentiality.) The following threat actions can cause

unauthorized disclosure:

A. "Exposure": A threat action whereby sensitive data is

directly released to an unauthorized entity. This includes:

a. "Deliberate Exposure": Intentional release of sensitive

data to an unauthorized entity.

b. "Scavenging": Searching through data residue in a system

to gain unauthorized knowledge of sensitive data.

c* "Human error": Human action or inaction that

unintentionally results in an entity gaining unauthorized

knowledge of sensitive data.

d* "Hardware/software error". System failure that results in

an entity gaining unauthorized knowledge of sensitive

data.

B. "Interception": A threat action whereby an unauthorized

entity directly accesses sensitive data traveling between

authorized sources and destinations. This includes:

a. "Theft": Gaining access to sensitive data by stealing a

shipment of a physical medium, such as a magnetic tape or

disk, that holds the data.

b. "Wiretapping (passive)": Monitoring and recording data

that is flowing between two points in a communication

system. (See: wiretapping.)

c. "Emanations analysis": Gaining direct knowledge of

communicated data by monitoring and resolving a signal

that is emitted by a system and that contains the data

but is not intended to communicate the data. (See:

emanation.)

C. "Inference": A threat action whereby an unauthorized entity

indirectly accesses sensitive data (but not necessarily the

data contained in the communication) by reasoning from

characteristics or byproducts of communications. This

includes:

a. Traffic analysis: Gaining knowledge of data by observing

the characteristics of communications that carry the

data. (See: (main Glossary entry for) traffic analysis.)

b. "Signals analysis": Gaining indirect knowledge of

communicated data by monitoring and analyzing a signal

that is emitted by a system and that contains the data

but is not intended to communicate the data. (See:

emanation.)

D. "Intrusion": A threat action whereby an unauthorized entity

gains access to sensitive data by circumventing a system's

security protections. This includes:

a. "Trespass": Gaining unauthorized physical access to

sensitive data by circumventing a system's protections.

b. "Penetration": Gaining unauthorized logical access to

sensitive data by circumventing a system's protections.

c. "Reverse engineering": Acquiring sensitive data by

disassembling and analyzing the design of a system

component.

d. Cryptanalysis: Transforming encrypted data into plaintext

without having prior knowledge of encryption parameters

or processes. (See: (main Glossary entry for)

cryptanalysis.)

2. "Deception" (a threat consequence): A circumstance or event

that may result in an authorized entity receiving false data

and believing it to be true. The following threat actions can

cause deception:

A. "Masquerade": A threat action whereby an unauthorized entity

gains access to a system or performs a malicious act by

posing as an authorized entity. (See: (main Glossary entry

for) masquerade attack.)

a. "Spoof": Attempt by an unauthorized entity to gain access

to a system by posing as an authorized user.

b. "Malicious logic": In context of masquerade, any

hardware, firmware, or software (e.g., Trojan horse) that

appears to perform a useful or desirable function, but

actually gains unauthorized access to system resources or

tricks a user into executing other malicious logic. (See:

(main Glossary entry for) malicious logic.)

B. "Falsification": A threat action whereby false data deceives

an authorized entity. (See: active wiretapping.)

a. "Substitution": Altering or replacing valid data with

false data that serves to deceive an authorized entity.

b. "Insertion": Introducing false data that serves to

deceive an authorized entity.

C. "Repudiation": A threat action whereby an entity deceives

another by falsely denying responsibility for an act. (See:

non-repudiation service, (main Glossary entry for)

repudiation.)

a. "False denial of origin": Action whereby the originator

of data denies responsibility for its generation.

b. "False denial of receipt": Action whereby the recipient

of data denies receiving and possessing the data.

3. "Disruption" (a threat consequence): A circumstance or event

that interrupts or prevents the correct operation of system

services and functions. (See: denial of service.) The following

threat actions can cause disruption:

A. "Incapacitation": A threat action that prevents or

interrupts system operation by disabling a system component.

a. "Malicious logic": In context of incapacitation, any

hardware, firmware, or software (e.g., logic bomb)

intentionally introduced into a system to destroy system

functions or resources. (See: (main Glossary entry for)

malicious logic.)

b. "Physical destruction": Deliberate destruction of a

system component to interrupt or prevent system

operation.

c* "Human error": Action or inaction that unintentionally

disables a system component.

d* "Hardware or software error": Error that causes failure

of a system component and leads to disruption of system

operation.

e* "Natural disaster": Any "act of God" (e.g., fire, flood,

earthquake, lightning, or wind) that disables a system

component. [FP031 section 2]

B. "Corruption": A threat action that undesirably alters system

operation by adversely modifying system functions or data.

a. "Tamper": In context of corruption, deliberate alteration

of a system's logic, data, or control information to

interrupt or prevent correct operation of system

functions.

b. "Malicious logic": In context of corruption, any

hardware, firmware, or software (e.g., a computer virus)

intentionally introduced into a system to modify system

functions or data. (See: (main Glossary entry for)

malicious logic.)

c* "Human error": Human action or inaction that

unintentionally results in the alteration of system

functions or data.

d* "Hardware or software error": Error that results in the

alteration of system functions or data.

e* "Natural disaster": Any "act of God" (e.g., power surge

caused by lightning) that alters system functions or

data. [FP031 section 2]

C. "Obstruction": A threat action that interrupts delivery of

system services by hindering system operations.

a. "Interference": Disruption of system operations by

blocking communications or user data or control

information.

b. "Overload": Hindrance of system operation by placing

excess burden on the performance capabilities of a system

component. (See: flooding.)

4. "Usurpation" (a threat consequence): A circumstance or event

that results in control of system services or functions by an

unauthorized entity. The following threat actions can cause

usurpation:

A. "Misappropriation": A threat action whereby an entity

assumes unauthorized logical or physical control of a system

resource.

a. "Theft of service": Unauthorized use of service by an

entity.

b. "Theft of functionality": Unauthorized acquisition of

actual hardware, software, or firmware of a system

component.

c. "Theft of data": Unauthorized acquisition and use of

data.

B. "Misuse": A threat action that causes a system component to

perform a function or service that is detrimental to system

security.

a. "Tamper": In context of misuse, deliberate alteration of

a system's logic, data, or control information to cause

the system to perform unauthorized functions or services.

b. "Malicious logic": In context of misuse, any hardware,

software, or firmware intentionally introduced into a

system to perform or control execution of an unauthorized

function or service.

c. "Violation of permissions": Action by an entity that

exceeds the entity's system privileges by executing an

unauthorized function.

$ thumbprint

(I) A pattern of curves formed by the ridges on the tip of a

thumb. (See: biometric authentication, fingerprint.)

(D) ISDs SHOULD NOT use this term as a synonym for "hash result"

because that meaning mixes concepts in a potentially misleading

way.

$ ticket

(I) A synonym for "capability". (See: Kerberos.)

server (ticket-granting agent) to authorize access to a system

resource for a limited time. Tickets have been implemented with

symmetric cryptography, but can also be implemented as attribute

certificates using asymmetric cryptography.

$ timing channel

See: (secondary definition under) covert channel.

$ TLS

See: Transport Layer Security. (See: TLSP.)

$ TLSP

See: Transport Layer Security Protocol. (See: TLS.)

$ token

1. (I) General usage: An object that is used to control access and

is passed between cooperating entities in a protocol that

synchronizes use of a shared resource. Usually, the entity that

currently holds the token has exclusive access to the resource.

2. (I) Authentication usage: A data object or a portable, user-

controlled, physical device used to verify an identity in an

authentication process. (See: authentication information, dongle.)

3. (I) Cryptographic usage: See: cryptographic token.

4. (O) SET usage: "A portable device [e.g., smart card or PCMCIA

card] specifically designed to store cryptographic information and

possibly perform cryptographic functions in a secure manner."

[SET2]

$ token backup

(I) A token management operation that stores sufficient

information in a database (e.g., in a CAW) to recreate or restore

a security token (e.g., a smart card) if it is lost or damaged.

$ token copy

(I) A token management operation that copies all the personality

information from one security token to another. However, unlike in

a token restore operation, the second token is initialized with

its own, different local security values such as PINs and storage

keys.

$ token management

(I) The process of initializing security tokens (e.g., see: smart

card), loading data into the tokens, and controlling the tokens

during their life cycle. May include performing key management and

certificate management functions; generating and installing PINs;

loading user personality data; performing card backup, card copy,

and card restore operations; and updating firmware.

$ token restore

(I) A token management operation that loads a security token with

data for the purpose of recreating (duplicating) the contents

previously held by that or another token.

$ token storage key

(I) A cryptography key used to protect data that is stored on a

security token.

$ top CA

(I) A CA that is the highest level (i.e., is the most trusted CA)

in a certification hierarchy. (See: root.)

$ top-level specification

(I) "A non-procedural description of system behavior at the most

abstract level; typically a functional specification that omits

all implementation details." [NCS04] (See: (discussion under)

security policy.)

- "Descriptive top-level specification": One that is written in a

natural language like English or an informal design notation.

- "Formal top-level specification": One that is written in a

formal mathematical language to enable theorems to be proven that

show that the specification correctly implements a set of formal

requirements or a formal security model. (See: correctness proof.)

$ traffic analysis

(I) Inference of information from observable characteristics of

data flow(s), even when the data is encrypted or otherwise not

directly available. Such characteristics include the identities

and locations of the source(s) and destination(s), and the

presence, amount, frequency, and duration of occurrence. (See:

wiretapping.)

(O) "The inference of information from observation of traffic

flows (presence, absence, amount, direction, and frequency)."

[I7498 Part 2]

$ traffic flow confidentiality

(I) A data confidentiality service to protect against traffic

analysis.

(O) "A confidentiality service to protect against traffic

analysis." [I7498 Part 2]

$ traffic padding

(I) "The generation of spurious instances of communication,

spurious data units, and/or spurious data within data units."

[I7498 Part 2]

$ tranquillity property

See: (secondary definition under) Bell-LaPadula Model.

$ Transmission Control Protocol (TCP)

(I) An Internet Standard protocol [R0793] that reliably delivers a

sequence of datagrams (discrete sets of bits) from one computer to

another in a computer network. (See: TCP/IP.)

that support internetwork applications. TCP assumes it can obtain

a simple, potentially unreliable datagram service (such as the

Internet Protocol) from the lower-layer protocols.

$ Transport Layer Security (TLS)

(I) TLS Version 1.0 is an Internet protocol [R2246] based-on and

very similar to SSL Version 3.0. (See: TLSP.)

the transport layer (OSI layer 4).

$ Transport Layer Security Protocol (TLSP)

(I) An end-to-end encryption protocol(ISO Standard 10736) that

provides security services at the bottom of OSI layer 4, i.e.,

directly above layer 3. (See: TLS.)

$ transport mode vs. tunnel mode

(I) IPsec usage: Two ways to apply IPsec protocols (AH and ESP) to

protect communications:

- "Transport mode": The protection applies to (i.e., the IPsec

protocol encapsulates) the packets of upper-layer protocols,

the ones that are carried above IP.

- "Tunnel mode": The protection applies to (i.e., the IPsec

protocol encapsulates) IP packets.

hosts. In a tunnel mode security association, each end may be

either a host or a gateway. Whenever either end of an IPsec

security association is a security gateway, the association is

required to be in tunnel mode.

$ trap door

(I) A hidden computer flaw known to an intruder, or a hidden

computer mechanism (usually software) installed by an intruder,

who can activate the trap door to gain access to the computer

without being blocked by security services or mechanisms. (See:

back door, Trojan horse.)

$ triple DES

(I) A block cipher, based on DES, that transforms each 64-bit

plaintext block by applying the Data Encryption Algorithm three

successive times, using either two or three different keys, for an

effective key length of 112 or 168 bits. [A9052] (See: DES.)

168-bit key, consisting of three independent 56-bit quantities

used by the Data Encryption Algorithm, and a 64-bit initialization

value. Each datagram contains an IV to ensure that each received

datagram can be decrypted even when other datagrams are dropped or

a sequence of datagrams is reordered in transit. [R1851]

$ triple-wrapped

(I) S/MIME usage: Data that has been signed with a digital

signature, and then encrypted, and then signed again. [R2634]

$ Trojan horse

(I) A computer program that appears to have a useful function, but

also has a hidden and potentially malicious function that evades

security mechanisms, sometimes by exploiting legitimate

authorizations of a system entity that invokes the program.

$ trust

1. (I) Information system usage: The extent to which someone who

relies on a system can have confidence that the system meets its

specifications, i.e., that the system does what it claims to do

and does not perform unwanted functions. (See: trust level.)

process or object, this Glossary (and industry usage) prefers the

term "trusted" to describe a system that operates as expected,

according to design and policy. When the trust can also be

guaranteed in some convincing way, such as through formal analysis

or code review, the system is termed "trustworthy"; this differs

from the ABA Guidelines definition (see: trustworthy system).

2. (I) PKI usage: A relationship between a certificate user and a

CA in which the user acts according to the assumption that the CA

creates only valid digital certificates.

(O) "Generally, an entity can be said to 'trust' a second entity

when it (the first entity) makes the assumption that the second

entity will behave exactly as the first entity expects. This trust

may apply only for some specific function. The key role of trust

in [X.509] is to describe the relationship between an entity and a

[certification] authority; an entity shall be certain that it can

trust the certification authority to create only valid and

reliable certificates." [X509]

$ trust chain

(D) ISDs SHOULD NOT use this term as a synonym for "certification

path" because it mixes concepts in a potentially misleading way.

(See: trust.)

$ trust-file PKI

(I) A non-hierarchical PKI in which each certificate user has a

local file (which is used by application software) of public-key

certificates that the user trusts as starting points (i.e., roots)

for certification paths. (See: hierarchical PKI, mesh PKI, root,

web of trust.)

file of trusted certificates, which often are self-signed

certificates. Users can add certificates to the file or delete

from it. The file may be directly managed by the user, or the

user's organization may manage it from a centralized server.

$ trust hierarchy

(D) ISDs SHOULD NOT use this term as a synonym for "certification

hierarchy" because this term mixes concepts (see: trust) in a

potentially misleading way and duplicates the meaning of another,

standardized term. (See: trust, web of trust.)

$ trust level

(I) A characterization of a standard of security protection to be

met by a computer system.

highest, they are D, C1, C2, B1, B2, B3, and A1. A trust level is

based not only on the presence of security mechanisms but also on

the use of systems engineering discipline to properly structure

the system and implementation analysis to ensure that the system

provides an appropriate degree of trust.

$ trusted

See: (discussion under) trust.

$ trusted certificate

(I) A certificate upon which a certificate user relies as being

valid without the need for validation testing; especially a

public-key certificate that is used to provide the first public

key in a certification path. (See: certification path, root

certificate, validation.)

certificate in a hierarchical PKI, (b) the certificate of the CA

that issued the user's own certificate in a mesh PKI, or (c)

any certificate accepted by the user in a trust-file PKI.

$ trusted computer system

(I) Multilevel security usage: "A system that employs sufficient

hardware and software assurance measures to allow its use for

simultaneous processing of a range of sensitive or classified

information." [NCS04] (See: (discussion under) trust.)

$ Trusted Computer System Evaluation Criteria (TCSEC)

(N) A standard for evaluating the security provided by operating

systems [CSC001, DOD1]. Informally called the "Orange Book"

because of the color of its cover; first document in the Rainbow

Series. (See: Common Criteria, (usage note under) Green Book,

Orange Book, trust level.)

$ trusted computing base (TCB)

(I) "The totality of protection mechanisms within a computer

system, including hardware, firmware, and software, the

combination of which is responsible for enforcing a security

policy." [NCS04] (See: (discussion of "trusted" under) trust.)

$ trusted distribution

(I) "A trusted method for distributing the TCB hardware, software,

and firmware components, both originals and updates, that provides

methods for protecting the TCB from modification during

distribution and for detection of any changes to the TCB that may

occur." [NCS04]

$ trusted key

(I) A public key upon which a user relies; especially a public key

that can be used as the first public key in a certification path.

(See: certification path, root key, validation.)

hierarchical PKI, (b) the key of the CA that issued the user's own

certificate in a mesh PKI, or (c) any key accepted by the user in

a trust-file PKI.

$ trusted path

(I) COMPUSEC usage: A mechanism by which a computer system user

can communicate directly and reliably with the trusted computing

base (TCB) and that can only be activated by the user or the TCB

and cannot be imitated by untrusted software within the computer.

[NCS04]

(I) COMSEC usage: A mechanism by which a person or process can

communicate directly with a cryptographic module and that can only

be activated by the person, process, or module, and cannot be

imitated by untrusted software within the module. [FP140]

$ trusted process

(I) A system process that has privileges that enable it to affect

the state of system security and that can, therefore, through

incorrect or malicious execution, violate the system's security

policy. (See: privileged process, (discussion of "trusted" under)

trust.)

$ trusted subnetwork

(I) A subnetwork containing hosts and routers that trust each

other not to engage in active or passive attacks. (There also is

an assumption that the underlying communication channels--e.g.,

telephone lines, or a LAN--are protected from attack by some

means.)

$ trusted system

See: (discussion under) trust, trusted computer system,

trustworthy system.

$ Trusted Systems Interoperability Group (TSIG)

(N) A forum of computer vendors, system integrators, and users

devoted to promoting interoperability of trusted computer systems.

TSIG meetings are open to all persons who are working in the

INFOSEC area.

$ trustworthy system

(O) ABA usage: "Computer hardware, software, and procedures that:

(a) are reasonably secure from intrusion and misuse; (b) provide a

reasonably reliable level of availability, reliability, and

correct operation; (c) are reasonably suited to performing their

intended functions; and (d) adhere to generally accepted security

principles." [ABA] This differs somewhat from other industry

usage. (See: (discussion of "trusted vs. trustworthy" under)

trust.)

$ TSIG

See: Trusted System Interoperability Group.

$ tunnel

(I) A communication channel created in a computer network by

encapsulating (carrying, layering) a communication protocol's data

packets in (on top of) a second protocol that normally would be

carried above, or at the same layer as, the first one. (See: L2TP,

VPN.)

layers; for example, a TCP connection between two hosts could

conceivably be tunneled through email messages across the

Internet. Most often, a tunnel is a logical point-to-point link--

i.e., an OSI layer 2 connection--created by encapsulating the

layer 2 protocol in a transport protocol (such as TCP), in a

network or internetwork layer protocol (such as IP), or in another

link layer protocol. Often, encapsulation is accomplished with an

extra, intermediate protocol, i.e., a tunneling protocol (such as

L2TP) that is layered between the tunneled layer 2 protocol and

the encapsulating protocol.

not supported by the network connecting them. Tunneling also can

enable a computer network to use the services of a second network

as though the second network were a set of point-to-point links

between the first network's nodes. (See: virtual private network.)

(O) SET usage: The name of a SET private extension that indicates

whether the CA or the payment gateway supports passing encrypted

messages to the cardholder through the merchant. If so, the

extension lists OIDs of symmetric encryption algorithms that are

supported.

$ tunnel mode

(I) IPsec usage: See: transport mode vs. tunnel mode.

$ two-person control

(I) The close surveillance and control of a system, process, or

materials (especially with regard to cryptography) at all times by

a minimum of two appropriately authorized persons, each capable of

detecting incorrect and unauthorized procedures with respect to

the tasks to be performed and each familiar with established

security requirements. (See: dual control, no-lone zone.)

$ Type I cryptography

(O) A cryptographic algorithm or device approved by NSA for

protecting classified information.

$ Type II cryptography

(O) A cryptographic algorithm or device approved by NSA for

protecting sensitive unclassified information (as specified in

section 2315 of Title 10 United States Code, or section 3502(2) of

Title 44, United States Code.)

$ Type III cryptography

(O) A cryptographic algorithm or device approved as a Federal

Information Processing Standard.

$ UDP

See: User Datagram Protocol.

$ unclassified

(I) Not classified.

$ unencrypted

(I) Not encrypted.

$ unforgeable

(I) Cryptographic usage: The property of a cryptographic data

structure (i.e., a data structure that is defined using one or

more cryptographic functions) that makes it computationally

infeasible to construct (i.e., compute) an unauthorized but

correct value of the structure without having knowledge of one of

more keys. (E.g., see: digital certificate.)

"unforgeable" means unable to be fraudulently created or

duplicated. In that broader sense, anyone can forge a digital

certificate containing any set of data items whatsoever by

generating the to-be-signed certificate and signing it with any

private key whatsoever. But for PKI purposes, the forged data

structure is invalid if it is not signed with the true private key

of the claimed issuer; thus, the forgery will be detected when a

certificate user uses the true public key of the claimed issuer to

verify the signature.

$ uniform resource identifier (URI)

(I) A type of formatted identifier that encapsulates the name of

an Internet object, and labels it with an identification of the

name space, thus producing a member of the universal set of names

in registered name spaces and of addresses referring to registered

protocols or name spaces. [R1630]

common practice, URIs include uniform resource locators [R2368]

and relative URLs, and may be URNs. [R1808]

$ uniform resource locator (URL)

(I) A type of formatted identifier that describes the access

method and location of an information resource object on the

Internet. [R1738]

access the named object. For example,

"ftp://bbnarchive.bbn.com/foo/bar/picture/cambridge.zip" is a URL.

The part before the colon specifies the access scheme or protocol,

and the part after the colon is interpreted according to that

access method. Usually, two slashes after the colon indicate the

host name of a server (written as a domain name). In an FTP or

HTTP URL, the host name is followed by the path name of a file on

the server. The last (optional) part of a URL may be either a

fragment identifier that indicates a position in the file, or a

query string.

$ uniform resource name (URN)

(I) A URI that has an institutional commitment to persistence and

availability.

$ untrusted process

(I) A system process that is not able to affect the state of

system security through incorrect or malicious operation, usually

because its operation is confined by a security kernel. (See:

trusted process.)

$ UORA

See: user-PIN ORA.

$ update

See: certificate update and key update.

$ URI

See: uniform resource identifier.

$ URL

See: uniform resource locator.

$ URN

See: uniform resource name.

$ user

(I) A person, organization entity, or automated process that

accesses a system, whether authorized to do so or not. (See:

[R2504].)

definition, because this term is used in many ways and can easily

be misunderstood.

$ User Datagram Protocol (UDP)

(I) An Internet Standard protocol [R0768] that provides a datagram

mode of packet-switched computer communication in an internetwork.

the underlying protocol. UDP enables application programs to send

transaction-oriented data to other programs with minimal protocol

mechanism. UDP does not provide reliable delivery, flow control,

sequencing, or other end-to-end services that TCP provides.

$ user identifier

(I) A character string or symbol that is used in a system to

uniquely name a specific user or group of users.

$ user PIN

(O) MISSI usage: One of two personal identification numbers that

control access to the functions and stored data of a FORTEZZA PC

card. Knowledge of the user PIN enables the card user to perform

the FORTEZZA functions that are intended for use by an end user.

(See: SSO PIN.)

$ user-PIN ORA (UORA)

(O) A MISSI organizational RA that operates in a mode in which the

ORA performs only the subset of card management functions that are

possible with knowledge of the user PIN for a FORTEZZA PC card.

(See: no-PIN ORA, SSO-PIN ORA.)

$ usurpation

See: (secondary definition under) threat consequence.

$ UTCTime

(N) The ASN.1 data type "UTCTime" contains a calendar date

(YYMMDD) and a time to a precision of either one minute (HHMM) or

one second (HHMMSS), where the time is either (a) Coordinated

Universal Time or (b) the local time followed by an offset that

enables Coordinated Universal Time to be calculated. Note: UTCTime

has the Year 2000 problem. (See: Coordinated Universal Time,

GeneralizedTime.)

$ v1 certificate

in its version 1 format, or an X.509 attribute certificate in its

version 1 format. However, many people who use this term are not

aware that X.509 specifies attribute certificates that do not

contain a public key. Therefore, ISDs MAY use this term as an

abbreviation for "version 1 X.509 public-key certificate", but

only after using the full term at the first instance.

(D) ISDs SHOULD NOT use this term as an abbreviation for "version

1 X.509 attribute certificate".

$ v1 CRL

(I) An abbreviation for "X.509 CRL in version 1 format".

term at its first occurrence and defining the abbreviation.

$ v2 certificate

(I) An abbreviation for "X.509 public-key certificate in version 2

format".

term at its first occurrence and defining the abbreviation.

$ v2 CRL

(I) An abbreviation for "X.509 CRL in version 2 format".

term at its first occurrence and defining the abbreviation.

$ v3 certificate

(I) An abbreviation for "X.509 public-key certificate in version 3

format".

term at its first occurrence and defining the abbreviation.

$ valid certificate

(I) A digital certificate for which the binding of the data items

can be trusted; one that can be validated successfully. (See:

validate vs. verify.)

$ valid signature

(D) ISDs SHOULD NOT use this term; instead, use "authentic

signature". This Glossary recommends saying "validate the

certificate" and "verify the signature"; therefore, it would be

inconsistent to say that a signature is "valid". (See: validate

vs. verify.)

$ validate vs. verify

what a certificate user does to make certain that a digital

certificate can be trusted. Usually, we say "verify the signature"

but say "validate the certificate"; i.e., we "verify" atomic

truths but "validate" data structures, relationships, and systems

that are composed of or depend on verified items. Too often,

however, verify and validate are used interchangeably.

ISDs SHOULD comply with the following two rules to ensure

consistency and to align Internet security terminology with

ordinary English:

- Rule 1: Use "validate" when referring to a process intended to

establish the soundness or correctness of a construct. (E.g.,

see: certificate validation.)

- Rule 2: Use "verify" when referring to a process intended to

test or prove the truth or accuracy of a fact or value. (E.g.,

see: authenticate.)

The rationale for Rule 1 is that "valid" derives from a word that

means "strong" in Latin. Thus, to validate means to make sure that

a construction is sound. A certificate user validates a public-key

certificate to establish trust in the binding that the certificate

asserts between an identity and a key. (To validate can also mean

to officially approve something; e.g., NIST validates

cryptographic modules for conformance with FIPS PUB 140-1.)

The rationale for Rule 2 is that "verify" derives from a word that

means "true" in Latin. Thus, to verify means to prove the truth of

an assertion by examining evidence or performing tests. To verify

an identity, an authentication process examines identification

information that is presented or generated. To validate a

certificate, a certificate user verifies the digital signature on

the certificate by performing calculations; verifies that the

current time is within the certificate's validity period; and may

need to validate a certification path involving additional

certificates.

$ validation

See: validate vs. verify.

$ validity period

(I) A data item in a digital certificate that specifies the time

period for which the binding between data items (especially

between the subject name and the public key value in a public-key

certificate) is valid, except if the certificate appears on a CRL

or the key appears on a CKL.

$ value-added network (VAN)

(I) A computer network or subnetwork (which is usually a

commercial enterprise) that transmits, receives, and stores EDI

transactions on behalf of its customers.

format translation, to EDI-to-FAX conversion, to integrated

business systems.

$ VAN

See: value-added network.

$ verification

1. System verification: The process of comparing two levels of

system specification for proper correspondence, such as comparing

a security policy with a top-level specification, a top-level

specification with source code, or source code with object code.

[NCS04]

2. Identification verification: Presenting information to

establish the truth of a claimed identity.

$ verify

See: validate vs. verify.

$ violation

See: security violation.

$ virtual private network (VPN)

(I) A restricted-use, logical (i.e., artificial or simulated)

computer network that is constructed from the system resources of

a relatively public, physical (i.e., real) network (such as the

Internet), often by using encryption (located at hosts or

gateways), and often by tunneling links of the virtual network

across the real network.

sites, each connected to the Internet by a firewall, the

corporation could create a VPN by (a) using encrypted tunnels to

connect from firewall to firewall across the Internet and (b) not

allowing any other traffic through the firewalls. A VPN is

generally less expensive to build and operate than a dedicated

real network, because the virtual network shares the cost of

system resources with other users of the real network.

$ virus

(I) A hidden, self-replicating section of computer software,

usually malicious logic, that propagates by infecting--i.e.,

inserting a copy of itself into and becoming part of--another

program. A virus cannot run by itself; it requires that its host

program be run to make the virus active.

$ VPN

See: virtual private network.

$ vulnerability

(I) A flaw or weakness in a system's design, implementation, or

operation and management that could be exploited to violate the

system's security policy.

not mean that the systems are too flawed to use. Not every threat

results in an attack, and not every attack succeeds. Success

depends on the degree of vulnerability, the strength of attacks,

and the effectiveness of any countermeasures in use. If the

attacks needed to exploit a vulnerability are very difficult to

carry out, then the vulnerability may be tolerable. If the

perceived benefit to an attacker is small, then even an easily

exploited vulnerability may be tolerable. However, if the attacks

are well understood and easily made, and if the vulnerable system

is employed by a wide range of users, then it is likely that there

will be enough benefit for someone to make an attack.

$ W3

See: World Wide Web.

$ war dialer

(I) A computer program that automatically dials a series of

telephone numbers to find lines connected to computer systems, and

catalogs those numbers so that a cracker can try to break into the

systems.

$ Wassenaar Arrangement

(N) The Wassenaar Arrangement on Export Controls for Conventional

Arms and Dual-Use Goods and Technologies is a global, multilateral

agreement approved by 33 countries in July 1996 to contribute to

regional and international security and stability, by promoting

information exchange concerning, and greater responsibility in,

transfers of arms and dual-use items, thus preventing

destabilizing accumulations. (See: International Traffic in Arms

Regulations.)

participating countries are Argentina, Australia, Austria,

Belgium, Bulgaria, Canada, Czech Republic, Denmark, Finland,

France, Germany, Greece, Hungary, Ireland, Italy, Japan,

Luxembourg, Netherlands, New Zealand, Norway, Poland, Portugal,

Republic of Korea, Romania, Russian Federation, Slovak Republic,

Spain, Sweden, Switzerland, Turkey, Ukraine, United Kingdom, and

United States. Participants meet on a regular basis in Vienna,

where the Arrangement has its headquarters.

Participating countries seek through their national policies to

ensure that transfers do not contribute to the development or

enhancement of military capabilities that undermine the goals of

the arrangement, and are not diverted to support such

capabilities. The countries maintain effective export controls for

items on the agreed lists, which are reviewed periodically to

account for technological developments and experience gained.

Through transparency and exchange of views and information,

suppliers of arms and dual-use items can develop common

understandings of the risks associated with their transfer and

assess the scope for coordinating national control policies to

combat these risks. Members provide semi-annual notification of

arms transfers, covering seven categories derived from the UN

denials of transfers of certain controlled dual-use items.

However, the decision to transfer or deny transfer of any item is

the sole responsibility of each participating country. All

measures undertaken with respect to the arrangement are in

accordance with national legislation and policies and are

implemented on the basis of national discretion.

$ watermarking

See: digital watermarking.

$ web of trust

(O) PGP usage: A trust-file PKI technique used in PGP for building

a file of validated public keys by making personal judgments about

being able to trust certain people to be holding properly

certified keys of other people. (See: certification hierarchy,

mesh PKI.)

$ web server

(I) A software process that runs on a host computer connected to

the Internet to respond to HTTP requests for documents from client

web browsers.

$ web vs. Web

1. (I) Capitalized: ISDs SHOULD capitalize "Web" when using the

term (as either a noun or an adjective) to refer specifically to

the World Wide Web. (Similarly, see: internet vs. Internet.)

2. (C) Not capitalized: ISDs SHOULD NOT capitalize "web" when

using the term (usually as an adjective) to refer generically to

technology--such as web browsers, web servers, HTTP, and HTML--

that is used in the Web or similar networks.

first instance of usage and SHOULD Use "Web" and "web" especially

carefully where confusion with the PGP "web of trust" is possible.

$ wiretapping

(I) An attack that intercepts and accesses data and other

information contained in a flow in a communication system.

connection to an electrical conductor that links two nodes, it is

now used to refer to reading information from any sort of medium

used for a link or even directly from a node, such as gateway or

subnetwork switch.

affect the flow; "passive wiretapping" only attempts to observe

the flow and gain knowledge of information it contains. (See:

active attack, end-to-end encryption, passive attack.)

$ work factor

(I) General security usage: The estimated amount of effort or time

that can be expected to be expended by a potential intruder to

penetrate a system, or defeat a particular countermeasure, when

using specified amounts of expertise and resources.

(I) Cryptography usage: The estimated amount of computing time and

power needed to break a cryptographic system.

$ World Wide Web ("the Web", WWW, W3)

(N) The global, hypermedia-based collection of information and

services that is available on Internet servers and is accessed by

browsers using Hypertext Transfer Protocol and other information

retrieval mechanisms. (See: web vs. Web, [R2084].)

$ worm

(I) A computer program that can run independently, can propagate a

complete working version of itself onto other hosts on a network,

and may consume computer resources destructively. (See: Morris

Worm, virus.)

$ wrap

(O) To use cryptography to provide data confidentiality service

for a data object. (See: encrypt, seal.)

(D) ISDs SHOULD NOT use this term with this definition because it

duplicates the meaning of other, standard terms. Instead, use

"encrypt" or use a term that is specific with regard to the

mechanism used.

$ WWW

See: World Wide Web.

$ X.400

(N) An ITU-T Recommendation [X400] that is one part of a joint

ITU-T/ISO multi-part standard (X.400-X.421) that defines the

Message Handling Systems. (The ISO equivalent is IS 10021, parts

1-7.) (See: Message Handling Systems.)

$ X.500

$ X.500 Directory

(N) An ITU-T Recommendation [X500] that is one part of a joint

ITU-T/ISO multi-part standard (X.500-X.525) that defines the X.500

Directory, a conceptual collection of systems that provide

distributed directory capabilities for OSI entities, processes,

applications, and services. (The ISO equivalent is IS 9594-1 and

related standards, IS 9594-x.) (See: directory vs. Directory,

X.509.)

Information Tree), and information is stored in directory entries.

Each entry is a collection of information about one object, and

each object has a DN. A directory entry is composed of attributes,

each with a type and one or more values. For example, if a PKI

uses the Directory to distribute certificates, then the X.509

public-key certificate of an end user is normally stored as a

value of an attribute of type "userCertificate" in the Directory

entry that has the DN that is the subject of the certificate.

$ X.509

(N) An ITU-T Recommendation [X509] that defines a framework to

provide and support data origin authentication and peer entity

authentication services, including formats for X.509 public-key

certificates, X.509 attribute certificates, and X.509 CRLs. (The

ISO equivalent is IS 9498-4.) (See: X.500.)

authentication based on a password, and strong authentication

based on a public-key certificate.

$ X.509 attribute certificate

(N) An attribute certificate in the version 1 (v1) format defined

by X.509. (The v1 designation for an X.509 attribute certificate

is disjoint from the v1 designation for an X.509 public-key

certificate, and from the v1 designation for an X.509 CRL.)

attribute certificate is a separate data structure from that

subject's public-key certificate. A subject may have multiple

attribute certificates associated with each of its public-key

certificates, and an attribute certificate may be issued by a

different CA than the one that issued the associated public-key

certificate.

items and has a digital signature that is computed from that

sequence. In addition to the signature, an attribute certificate

contains items 1 through 9 listed below:

1. version Identifies v1.

2. subject Is one of the following:

2a. baseCertificateID - Issuer and serial number of an

X.509 public-key certificate.

2b. subjectName - DN of the subject.

3. issuer DN of the issuer (the CA who signed).

4. signature OID of algorithm that signed the cert.

5. serialNumber Certificate serial number;

an integer assigned by the issuer.

6. attCertValidityPeriod Validity period; a pair of UTCTime

values: "not before" and "not after".

7. attributes Sequence of attributes describing the

subject.

8. issuerUniqueId Optional, when a DN is not sufficient.

9. extensions Optional.

$ X.509 authority revocation list

(N) An ARL in one of the formats defined by X.509--version 1 (v1)

or version 2 (v2). A specialized kind of certificate revocation

list.

$ X.509 certificate

(N) Either an X.509 public-key certificate or an X.509 attribute

certificate.

recommended here. However, some who use the term may not be aware

that X.509 specifies attribute certificates that do not contain a

public key. Even among those who are aware, this term is commonly

used as an abbreviation to mean "X.509 public-key certificate".

ISDs MAY use the term as an abbreviation for "X.509 public-key

certificate", but only after using the full term at the first

instance.

(D) ISDs SHOULD NOT use this term as an abbreviation to mean

"X.509 attribute certificate".

$ X.509 certificate revocation list (CRL)

(N) A CRL in one of the formats defined by X.509--version 1 (v1)

or version 2 (v2). (The v1 and v2 designations for an X.509 CRL

are disjoint from the v1 and v2 designations for an X.509 public-

key certificate, and from the v1 designation for an X.509

attribute certificate.) (See: certificate revocation.)

certificate, but note that an X.509 CRL does meet this Glossary's

definition of "digital certificate". Like a digital certificate,

an X.509 CRL makes an assertion and is signed by a CA. But instead

of binding a key or other attributes to a subject, an X.509 CRL

asserts that certain previously-issued X.509 certificates have

been revoked.

digital signature computed on that sequence. In addition to the

signature, both v1 and v2 contain items 2 through 6b listed below.

Version 2 contains item 1 and may optionally contain 6c and 7.

1. version Optional. If present, identifies v2.

2. signature OID of the algorithm that signed CRL.

3. issuer DN of the issuer (the CA who signed).

4. thisUpdate A UTCTime value.

5. nextUpdate A UTCTime value.

6. revokedCertificates 3-tuples of 6a, 6b, and (optional) 6c:

6a. userCertificate A certificate's serial number.

6b. revocationDate UTCTime value for the revocation date.

6c. crlEntryExtensions Optional.

7. crlExtensions Optional.

$ X.509 public-key certificate

(N) A public-key certificate in one of the formats defined by

X.509--version 1 (v1), version 2 (v2), or version 3 (v3). (The v1

and v2 designations for an X.509 public-key certificate are

disjoint from the v1 and v2 designations for an X.509 CRL, and

from the v1 designation for an X.509 attribute certificate.)

items and has a digital signature computed on that sequence. In

addition to the signature, all three versions contain items 1

through 7 listed below. Only v2 and v3 certificates may also

contain items 8 and 9, and only v3 may contain item 10.

1. version Identifies v1, v2, or v3.

2. serialNumber Certificate serial number;

an integer assigned by the issuer.

3. signature OID of algorithm that was used to

sign the certificate.

4. issuer DN of the issuer (the CA who signed).

5. validity Validity period; a pair of UTCTime

values: "not before" and "not after".

6. subject DN of entity who owns the public key.

7. subjectPublicKeyInfo Public key value and algorithm OID.

8. issuerUniqueIdentifier Defined for v2, v3; optional.

9. subjectUniqueIdentifier Defined for v2, v2; optional.

10. extensions Defined only for v3; optional.

$ XTACACS

See: (secondary definition under) Terminal Access Controller (TAC)

Access Control System.

$ Yellow Book

(D) ISDs SHOULD NOT use this term as a synonym for "Computer

Security Requirements: Guidance for Applying the Department of

Defense Trusted Computer System Evaluation Criteria in Specific

Environments" [CSC3]. Instead, use the full proper name of the

document or, in subsequent references, a conventional

abbreviation. (See: (usage note under) Green Book, Rainbow

Series.)

$ zeroize

(I) Use erasure or other means to render stored data unusable and

unrecoverable, particularly a key stored in a cryptographic module

or other device.

(O) Erase electronically stored data by altering the contents of

the data storage so as to prevent the recovery of the data.

[FP140]

4. References

This Glossary focuses on the Internet Standards Process. Therefore,

this set of references emphasizes international, governmental, and

industry standards documents; only a few other texts are listed. RFCs

are listed, but not Internet-Drafts, because the latter are not an

archival document series and should not be cited or quoted in an RFC.

[A3092] American National Standards Institute, "American National

Standard Data Encryption Algorithm", ANSI X3.92-1981, 30 Dec

1980.

[A9009] ---, "Financial Institution Message Authentication

(Wholesale)", ANSI X9.9-1986, 15 Aug 1986.

[A9017] ---, "Financial Institution Key Management (Wholesale)",

X9.17, 4 Apr 1985. [Defines procedures for the manual and

automated management of keying material and uses DES to

provide key management for a variety of operational

environments.]

[A9042] ---, "Public key Cryptography for the Financial Service

Industry: Agreement of Symmetric Keys Using Diffie-Hellman

and MQV Algorithms", X9.42, 29 Jan 1999.

[A9052] ---, "Triple Data Encryption Algorithm Modes of Operation",

X9.52-1998, ANSI approval 9 Nov 1998.

[A9062] ---, "Public Key Cryptography for the Financial Services

Industry: The Elliptic Curve Digital Signature Algorithm

(ECDSA)", X9.62-1998, ANSI approval 7 Jan 1999.

[ABA] American Bar Association, "Digital Signature Guidelines:

Legal Infrastructure for Certification Authorities and

Secure Electronic Commerce", Chicago, IL, 1 Aug 1996.

[ACM] Association for Computing Machinery, "Communications of the

ACM", Jul 1998 issue with: Minerva M. Yeung, "Digital

Watermarking"; Nasir Memom and Ping Wah Wong, "Protecting

Digital Media Content"; and Scott Craver, Boon-Lock Yeo, and

Minerva Yeung, "Technical Trials and Legal Tribulations".

[Army] U.S. Army Corps of Engineers, "Electromagnetic Pulse (EMP)

and Tempest Protection for Facilities", EP 1110-3-2, 31 Dec

1990.

[B7799] British Standards Institution, "Information Security

Management, Part 1: Code of Practice for Information

Security Management", BS 7799-1:1999, effective 15 May 1999.

---, ---, "Part 2: Specification for Information Security

Management Systems", BS 7799-2:1999, effective 15 May 1999.

[Bell] D. E. Bell and L. J. LaPadula, "Secure Computer Systems:

Mathematical Foundations and Model", M74-244, The MITRE

Corporation, Bedford, MA, May 1973. (Available as AD-771543,

National Technical Information Service, Springfield, VA.)

[CCIB] Common Criteria Implementation Board, "Common Criteria for

Information Technology Security Evaluation, Part 1:

Introduction and General Model", ver. 2.1, CCIB-99-01, Aug

1999.

[CIPSO] Trusted Systems Interoperability Working Group, "Common IP

Security Option", ver. 2.3, 9 Mar 1993. [A "work in

progress" that is probably defunct.]

[CSC1] U.S. Department of Defense Computer Security Center,

"Department of Defense Trusted Computer System Evaluation

Criteria", CSC-STD-001-83, 15 Aug 1983. (Superseded by

[DOD1].)

[CSC2] ---, "Department of Defense Password Management Guideline",

CSC-STD-002-85, 12 Apr 1985.

[CSC3] ---, "Computer Security Requirements: Guidance for Applying

the Department of Defense Trusted Computer System Evaluation

Criteria in Specific Environments", CSC-STD-003-85, 25 Jun

1985.

[CSOR] U.S. Department of Commerce, "General Procedures for

Registering Computer Security Objects", National Institute

of Standards Interagency Report 5308, Dec 1993.

[Denn] D. E. Denning, "A Lattice Model of Secure Information Flow",

in "Communications of the ACM", vol. 19, no. 5, May 1976,

pp. 236-243.

[DH76] W. Diffie and M. H. Hellman, "New Directions in

Cryptography" in "IEEE Transactions on Information Theory",

vol. IT-22, no. 6, Nov 1976, pp. 644-654.

[DOD1] U.S. Department of Defense, "Department of Defense Trusted

Computer System Evaluation Criteria", DoD 5200.28-STD, 26

Dec 1985. (Supersedes [CSC1].)

[DOD2] ---, Directive 5200.28, "Security Requirements for Automated

Information Systems (AISs)", 21 Mar 1988.

[DOD3] ---, "X.509 Certificate Policy", ver. 2, Mar 1999.

[DOD4] ---, "NSA Key Recovery Assessment Criteria", 8 Jun 1998.

[ElGa] T. El Gamal, "A Public-Key Cryptosystem and a Signature

Scheme Based on Discrete Logarithms" in "IEEE Transactions

on Information Theory", vol. IT-31, no. 4, 1985, pp. 469-

472.

[EMV1] Europay International S.A., MasterCard International

Incorporated, and Visa International Service Association,

"EMV '96 Integrated Circuit Card Specification for Payment

Systems", ver. 3.1.1, 31 May 1998.

[EMV2] ---, "EMV '96 Integrated Circuit Card Terminal Specification

for Payment Systems", ver. 3.1.1, 31 May 1998.

[EMV3] ---, EMV '96 Integrated Circuit Card Application

Specification for Payment Systems", ver. 3.1.1, 31 May 1998.

[For94] W. Ford, "Computer Communications Security: Principles,

Standard Protocols and Techniques", ISBN 0-13-799453-2,

1994.

[For97] W. Ford and M. Baum, "Secure Electronic Commerce: Building

the Infrastructure for Digital Signatures and Encryption",

ISBN 0-13-476342-4, 1994.

[FP031] U.S. Department of Commerce, "Guidelines for Automatic Data

Processing Physical Security and Risk Management", Federal

Information Processing Standards Publication (FIPS PUB) 31,

Jun 1974.

[FP039] ---, "Glossary for Computer Systems Security", FIPS PUB 39,

15 Feb 1976.

[FP046] ---, "Data Encryption Standard (DES)", FIPS PUB 46-2, 30 Dec

1993.

[FP081] ---, "DES Modes of Operation", FIPS PUB 81, 2 Dec 1980.

[FP102] ---, "Guideline for Computer Security Certification and

Accreditation", FIPS PUB 102, 27 Sep 1983.

[FP113] ---, "Computer Data Authentication", FIPS PUB 113, 30 May

1985.

[FP140] ---, "Security Requirements for Cryptographic Modules", FIPS

PUB 140-1, 11 Jan 1994.

[FP151] ---, "Portable Operating System Interface (POSIX)--System

Application Program Interface [C Language]", FIPS PUB 151-2,

12 May 1993

[FP180] ---, "Secure Hash Standard", FIPS PUB 180-1, 17 Apr 1995.

[FP185] ---, "Escrowed Encryption Standard", FIPS PUB 185, 9 Feb

1994.

[FP186] ---, "Digital Signature Standard (DSS)", FIPS PUB 186, 19

May 1994.

[FP188] ---, "Standard Security Label for Information Transfer",

FIPS PUB 188, 6 Sep 1994.

[FPDAM] Collaborative ITU and ISO/IEC meeting on the Directory,

"Final Proposed Draft Amendment on Certificate Extensions",

April 1999. (This draft proposes changes to [X.509].)

[FPKI] U.S. Department of Commerce, "Public Key Infrastructure

(PKI) Technical Specifications: Part A--Technical Concept of

Operations", National Institute of Standards, 4 Sep 1998.

[I3166] International Standards Organization, "Codes for the

Representation of Names of countries and Their Subdivisions

--Part 1: Country Codes", ISO 3166-1:1997.

---, --- "Part 2: Country Subdivision Codes", ISO/DIS 3166-

---, --- "Part 3: Codes for Formerly Used Names of

Countries", ISO/DIS 3166-3.

[I7498] ---, "Information Processing Systems--Open Systems

Interconnection Reference Model--[Part 1:] Basic Reference

Model", ISO/IEC 7498-1. (Equivalent to ITU-T Recommendation

X.200.)

---, --- "Part 2: Security Architecture", ISO/IEC 7499-2.

---, --- "Part 4: Management Framework", ISO/IEC 7498-4.

[I7812] ---, "Identification cards--Identification of Issuers--Part

1: Numbering System", ISO/IEC 7812-1:1993

---, --- "Part 2: Application and Registration Procedures",

ISO/IEC 7812-2:1993.

[I9945] ---, "Portable Operating System Interface for Computer

Environments", ISO/IEC 9945-1:1990.

[I15408] ---, "Information Technology--Security Techniques--

Evaluation criteria for IT Security--Part 1: Introduction

and General Model", ISO/IEC 15408-1:1999.

[ITSEC] "Information Technology Security Evaluation Criteria

(ITSEC): Harmonised Criteria of France, Germany, the

Netherlands, and the United Kingdom", ver. 1.2, U.K.

Department of Trade and Industry, Jun 1991.

[Kahn] David Kahn, "The Codebreakers: The Story of Secret Writing",

The Macmillan Company, New York, 1967.

[Knuth] D. E. Knuth, Chapter 3 ("Random Numbers") in Volume 2

("Seminumerical Algorithms") of "The Art of Computer

Programming", Addison-Wesley, Reading, MA, 1969.

[Kuhn] Markus G. Kuhn and Ross J. Anderson, "Soft Tempest: Hidden

Data Transmission Using Electromagnetic Emanations", in

David Aucsmith, ed., "Information Hiding, Second

International Workshop, IH'98", Portland, Oregon, USA, 15-17

Apr 1998, LNCS 1525, Springer-Verlag, ISBN 3-540-65386-4,

pp. 124-142.

[MISPC] U.S. Department of Commerce, "Minimum Interoperability

Specification for PKI Components (MISPC), Version 1",

National Institute of Standards Special Publication 800-15,

Sep 1997.

[NCS01] National Computer Security Center, "A Guide to Understanding

Audit in Trusted Systems", NCSC-TG-001, 1 Jun 1988. (Part of

the Rainbow Series.)

[NCS04] ---, "Glossary of Computer Security Terms", NCSC-TG-004,

ver. 1, 21 Oct 1988. (Part of the Rainbow Series.)

[NCS05] ---, "Trusted Network Interpretation of the Trusted Computer

System Evaluation Criteria", NCSC-TG-005, ver. 1, 31 Jul

1987. (Part of the Rainbow Series.)

[NCS25] ---, "A Guide to Understanding Data Remanence in Automated

Information Systems", NCSC-TG-025, ver. 2, Sep 1991. (Part

of the Rainbow Series.)

[NIST] National Institute of Standards and Technology, "SKIPJACK

and KEA Algorithm Specifications", ver. 2, 29 May 1998.

(http://csrc.nist.gov/encryption/skipjack-kea.htm)

[PGP] Simson Garfinkel, "PGP: Pretty Good Privacy", O'Reilly &

Associates, Inc., Sebastopol, CA, 1995.

[PKCS] Burton S. Kaliski, Jr., "An Overview of the PKCS Standards",

RSA Data Security, Inc., 3 Jun 1991.

[PKC07] RSA Laboratories, "PKCS #7: Cryptographic Message Syntax

Standard", ver. 1.5, RSA Laboratories Technical Note, 1 Nov

1993.

[PKC10] ---, "PKCS #10: Certification Request Syntax Standard", ver.

1.0, RSA Laboratories Technical Note, 1 Nov 1993.

[PKC11] ---, "PKCS #11: Cryptographic Token Interface Standard",

ver. 1.0, 28 Apr 1995.

[R0768] Postel, J., "User Datagram Protocol", STD 6, RFC768, August

1980.

[R0791] Postel, J., "Internet Protocol", STD 5, RFC791, September

1981.

[R0792] Postel, J., "Internet Control Message Protocol", STD 5, RFC

792, September 1981. [See: RFC1885.]

[R0793] Postel, J., ed., "Transmission Control Protocol", STD 7, RFC

793, September 1981.

[R0821] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC

821, August 1982.

[R0822] Crocker, D., "Standard for the Format of ARPA Internet Text

Messages", STD 11, RFC822, August 1982.

[R0854] Postel, J. and J. Reynolds, "TELNET Protocol Specification",

STD 8, RFC854, May 1983.

[R0959] Postel, J. and J. Reynolds, "File Transfer Protocol (FTP)",

STD 9, RFC959, October 1985.

[R1034] Mockapetris, P., "Domain Names--Concepts and Facilities",

STD 13, RFC1034, November 1987.

[R1157] Case, J., Fedor, M., Schoffstall, M. and J. Davin, "A Simple

Network Management Protocol (SNMP)" [version 1], STD 15, RFC

1157, May 1990.

[R1208] Jacobsen O. and D. Lynch, "A Glossary of Networking Terms",

RFC1208, March 1991.

[R1319] Kaliski, B., "The MD2 Message-Digest Algorithm", RFC1319,

April 1992.

[R1320] Rivest, R., "The MD4 Message-Digest Algorithm", RFC1320,

April 1992.

[R1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC1321,

April 1992.

[R1334] Lloyd, B. and W. Simpson, "PPP Authentication Protocols",

RFC1334, October 1992.

[R1413] St. Johns, M., "Identification Protocol", RFC1413, February

1993.

[R1421] Linn, J., "Privacy Enhancement for Internet Electronic Mail,

Part I: Message Encryption and Authentication Procedures",

RFC1421, February 1993.

[R1422] Kent, S., "Privacy Enhancement for Internet Electronic Mail,

Part II: Certificate-Based Key Management", RFC1422,

February 1993.

[R1455] Eastlake, D., "Physical Link Security Type of Service", RFC

1455, May 1993.

[R1457] Housley, R., "Security Label Framework for the Internet",

RFC1457, May 1993.

[R1492] Finseth, C., "An Access Control Protocol, Sometimes Called

TACACS", RFC1492, July 1993.

[R1507] Kaufman, C., "DASS: Distributed Authentication Security

Service", RFC1507, September 1993.

[R1510] Kohl, J. and C. Neuman, "The Kerberos Network Authentication

Service (V5)", RFC1510, September 1993.

[R1591] Kohl, J. and C. Neuman, "Domain Name System Structure and

Delegation", March 1994.

[R1630] Berners-Lee, T., "Universal Resource Identifiers in WWW",

RFC1630, June 1994.

[R1661] Simpson, W., ed., " The Point-to-Point Protocol (PPP)", STD

51, RFC1661, July 1994.

[R1731] Myers, J., "IMAP4 Authentication Mechanisms", RFC1731,

December 1994.

[R1734] Myers, J., "POP3 AUTHentication Command", RFC1734, December

1994.

[R1738] Myers, J., Masinter, L. and M. McCahill, ed's., "Uniform

Resource Locators (URL)", RFC1738, December 1994.

[R1750] Eastlake, D., Crocker, S. and J. Schiller, "Randomness

Recommendations for Security", RFC1750, December 1994.

[R1777] Yeong, W., Howes, T. and S. Kille, "Lightweight Directory

Access Protocol", RFC1777, March 1995.

[R1808] Fielding, R., "Relative Uniform Resource Locators", RFC

1808, June 1995.

[R1824] Danisch, H., "The Exponential Security System TESS: An

Identity-Based Cryptographic Protocol for Authenticated Key-

Exchange (E.I.S.S.-Report 1995/4)", RFC1824, August 1995.

[R1828] Metzger, P. and W. Simpson, "IP Authentication using Keyed

MD5", RFC1828, August 1995.

[R1829] Karn, P., Metzger, P. and W. Simpson, "The ESP DES-CBC

Transform", RFC1829, August 1995.

[R1848] Crocker, S., Freed, N., Galvin, J. and S. Murphy, "MIME

Object Security Services", RFC1848, October 1995.

[R1851] Karn, P., Metzger, P. and W. Simpson, "The ESP Triple DES

Transform", RFC1851, September 1995.

[R1866] Berners-Lee, T., "Hypertext Markup Language--2.0", RFC1866,

November 1995.

[R1885] Conta, A. and S. Deering, "Internet Control Message Protocol

(ICMPv6) for the Internet Protocol Version 6 (IPv6)

Specification", RFC1885, December 1995.

[R1928] Leech, M., Ganis, M., Lee, Y., Kuris, R., Koblas, D. and L.

Jones, "SOCKS Protocol Version 5", RFC1928, March 1996.

[R1938] Haller, N. and C. Metzion, "A One-Time Password System", RFC

1938, May 1996.

[R1939] Myers, J. and M. Rose, "Post Office Protocol - Version 3",

STD 53, RFC1939, May 1996.

[R1958] Carpenter, B., ed., "Architectural Principles of the

Internet", RFC1958, June 1996.

[R1983] Malkin, G., ed., "Internet Users' Glossary", FYI 18, RFC

1983, August 1996.

[R1994] Simpson, W. "PPP Challenge Handshake Authentication Protocol

(CHAP)", RFC1994, August 1996.

[R2023] Postel, J. and J. Reynolds, "Instructions to RFCAuthors",

RFC2023, October 1997.

[R2026] Bradner, S., "The Internet Standards Process--Revision 3",

BCP 9, RFC2026, March 1994.

[R2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail

Extensions (MIME) Part One: Format of Internet Message

Bodies", RFC2045, November 1996.

[R2060] Crispin, M., "Internet Message Access Protocol--Version 4

Revision 1", RFC2060, December 1996.

[R2065] Eastlake, D., 3rd, "Domain Name System Security Extensions",

RFC2065, January 1997.

[R2078] Linn, J., "Generic Security Service Application Program

Interface, Version 2", RFC2078, January 1997.

[R2084] Bossert, G., Cooper, S. and W. Drummond, "Considerations for

Web Transaction Security", RFC2084, January 1997.

[R2104] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed-

Hashing for Message Authentication", RFC2104, February

1997.

[R2119] Bradner, S., "Key Words for Use in RFCs To Indicate

Requirement Levels", BCP 14, RFC2119, March 1997.

[R2138] Rigney, C., Rubens, A., Simpson, W. and S. Willens, "Remote

Authentication Dial In User Service (RADIUS)", RFC2138,

April 1997.

[R2137] Eastlake, D., "Secure Domain Name System Dynamic Update",

RFC2137, April 1997.

[R2179] Gwinn, A., "Network Security For Trade Shows", RFC2179,

July 1997.

[R2195] Klensin, J., Catoe, R. and P. Krumviede, "IMAP/POP AUTHorize

Extension for Simple Challenge/Response", RFC2195, Sepember

1997.

[R2196] Fraser, B., "Site Security Handbook", FYI 8, RFC2196,

Sepember 1997.

[R2202] Cheng, P. and R. Glenn, "Test Cases for HMAC-MD5 and HMAC-

SHA-1", RFC2202, Sepember 1997.

[R2222] Myers, J., "Simple Authentication and Security Layer

(SASL)", RFC2222, October 1997.

[R2223] Postel, J., "Instructions to RFCAuthors", RFC2223, October

1997.

[R2246] Dierks, T. and C. Allen, "The TLS Protocol, Version 1.0",

RFC2246, January 1999.

[R2284] Blunk, L. and J. Vollbrecht, "PPP Extensible Authentication

Protocol (EAP)", RFC2284, March 1998.

[R2315] Kaliski, B., "PKCS #7: Cryptographic Message Syntax, Version

1.5", RFC2315, March 1998.

[R2323] Ramos, A., "IETF Identification and Security Guidelines",

RFC2323, 1 April 1998. [Intended for humorous entertainment

("please laugh loud and hard"); does not contain serious

security information.]

[R2350] Brownlee, N. and E. Guttman, "Expectations for Computer

Security Incident Response", RFC2350, June 1998.

[R2356] Montenegro, C. and V. Gupta, "Sun's SKIP Firewall Traversal

for Mobile IP", RFC2356, June 1998.

[R2373] Hinden, R. and S. Deering, "IP Version 6 Addressing

Architecture", RFC2373, July 2998.

[R2401] Kent, S. and R. Atkinson, "Security Architecture for the

Internet Protocol", RFC2401, November 1998.

[R2402] Kent, S. and R. Atkinson, "IP Authentication Header", RFC

2402, November 1998.

[R2403] Madson, C. and R. Glenn, "The Use of HMAC-MD5-96 within ESP

and AH", RFC2403, November 1998.

[R2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within

ESP and AH", RFC2404, November 1998.

[R2405] Madson, C. and N. Doraswamy, "The ESP DES-CBC Cipher

Algorithm With Explicit IV", RFC2405, November 1998.

[R2406] Kent, S. and R. Atkinson, "IP Encapsulating Security Payload

(ESP)", RFC2406, November 1998.

[R2407] Piper, D., "The Internet IP Security Domain of

Interpretation for ISAKMP", RFC2407, November 1998.

[R2408] Maughan, D., Schertler, M., Schneider, M. and J. Turner,

"Internet Security Association and Key Management Protocol

(ISAKMP)", RFC2408, November 1998.

[R2409] Harkins, D. and D. Carrel, "The Internet Key Exchange

(IKE)", RFC2409, November 1998.

[R2410] Glenn, R. and S. Kent, "The NULL Encryption Algorithm and

Its Use With IPsec", RFC2410, November 1998.

[R2412] Orman, H., "The OAKLEY Key Determination Protocol", RFC

2412, November 1998.

[R2451] Pereira, R. and R. Adams, "The ESP CBC-Mode Cipher

Algorithms", RFC2451, November 1998.

[R2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6

(IPv6) Specification", RFC2460, December 1998.

[R2504] Guttman, E., Leong, L. and G. Malkin, "Users' Security

Handbook", RFC2504, February 1999.

[R2510] Adams, C. and S. Farrell, "Internet X.509 Public Key

Infrastructure Certificate Management Protocols", RFC2510,

March 1999.

[R2527] Chokhani, S. and W. Ford, "Internet X.509 Public Key

Infrastructure, Certificate Policy and Certification

Practices Framework", RFC2527, March 1999.

[R2536] EastLake, D., "DSA KEYs and SIGs in the Domain Name System

(DNS)", RFC2536, March 1999.

[R2570] Case, J., Mundy, R., Partain, D. and B. Stewart,

"Introduction to Version 3 of the Internet-Standard Network

Management Framework", RFC2570, April 1999.

[R2574] Blumenthal, U. and B. Wijnen, "User-based Security Model

(USM) for Version 3 of the Simple Network Management

Protocol (SNMPv3)", RFC2574, April 1999.

[R2612] Adams, C. and J. Gilchrist, "The CAST-256 Encryption

Algorithm", RFC2612, June 1999.

[R2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter,

L., Leach, P. and T. Berners-Lee, "Hypertext Transfer

Protocol-- HTTP/1.1", RFC2616, June 1999.

[R2628] Smyslov, V., "Simple Cryptographic Program Interface", RFC

2628, June 1999.

[R2630] Housley, R., "Cryptographic Message Syntax", RFC2630, June

1999.

[R2631] Rescorla, E., "Diffie-Hellman Key Agreement Method", RFC

2631, June 1999.

[R2633] Ramsdell, B., ed., "S/MIME Version 3 Message Specification",

RFC2633, June 1999.

[R2634] Hoffman, P., ed., "Enhanced Security Services for S/MIME",

RFC2634, June 1999.

[R2635] Hambridge, S. and A. Lunde, "Don't Spew: A Set of Guidelines

for Mass Unsolicited Mailings and Postings", RFC2635, June

1999.

[Raym] E. S. Raymond, ed., "The On-Line Hacker Jargon File", ver.

4.0.0, 24 Jul 1996. (Also available as "The New Hacker's

Dictionary", 2nd edition, MIT Press, Sep 1993, ISBN 0-262-

18154-1. See: http://www.tuxedo.org/jargon/ for the latest

version.)

[Russ] D. Russell and G. T. Gangemi Sr., Chapter 10 ("TEMPEST") in

"Computer Security Basics", ISBN 0-937175-71-4, 1991.

[Schn] B. Schneier, "Applied Cryptography", John Wiley & Sons,

Inc., New York, 1994.

[SDNS3] U.S. Department of Defense, National Security Agency,

"Secure Data Network Systems, Security Protocol 3 (SP3)",

document SDN.301, Revision 1.5, 15 May 1989.

[SDNS4] ---, ---, "Security Protocol 4 (SP4)", document SDN.401,

Revision 1.2, 12 Jul 1988.

[SDNS7] ---, ---, "Secure data Network System, Message Security

Protocol (MSP)", document SDN.701, Revision 4.0, 7 Jun 1996,

with Corrections to Message Security Protocol, SDN.701, Rev

4.0", 96-06-07, 30 Aug, 1996.

[SET1] MasterCard and Visa, "SET Secure Electronic Transaction

Specification, Book 1: Business Description", ver. 1.0, 31

May 1997.

[SET2] ---, "SET Secure Electronic Transaction Specification, Book

2: Programmer's Guide", ver. 1.0, 31 May 1997.

[Stei] J. Steiner, C. Neuman, and J. Schiller, "Kerberos: An

Authentication Service for Open Network Systems" in "Usenix

Conference Proceedings", Feb 1988.

[X400] International Telecommunications Union--Telecommunication

Standardization Sector (formerly "CCITT"), Recommendation

X.400, "Message Handling Services: Message Handling System

and Service Overview".

[X500] ---, Recommendation X.500, "Information Technology--Open

Systems Interconnection--The Directory: Overview of

Concepts, Models, and Services". (Equivalent to ISO 9594-1.)

[X501] ---, Recommendation X.501, "Information Technology--Open

Systems Interconnection--The Directory: Models".

[X509] ---, Recommendation X.509, "Information Technology--Open

Systems Interconnection--The Directory: Authentication

Framework". (Equivalent to ISO 9594-8.)

[X519] ---, Recommendation X.519, "Information Technology--Open

Systems Interconnection--The Directory: Protocol

Specifications".

[X520] ---, Recommendation X.520, "Information Technology--Open

Systems Interconnection--The Directory: Selected Attribute

Types".

[X680] ---, Recommendation X.680, "Information Technology--Abstract

Syntax Notation One (ASN.1)--Specification of Basic

Notation", 15 Nov 1994. (Equivalent to ISO/IEC 8824-1.)

[X690] ---, Recommendation X.690, "Information Technology--ASN.1

Encoding Rules--Specification of Basic Encoding Rules (BER),

Canonical Encoding Rules (CER) and Distinguished Encoding

Rules (DER)", 15 Nov 1994. (Equivalent to ISO/IEC 8825-1.)

5. Security Considerations

This document only defines security terms and recommends how to use

them. It does not describe in detail the vulnerabilities of, threats

to, or mechanisms that protect specific Internet protocols.

6. Acknowledgments

Pat Cain, Mike Kong, and Charles Lynn provided meticulous comments on

an early draft.

7. Author's Address

Please address all comments to:

Robert W. Shirey GTE / BBN Technologies

EMail: rshirey@bbn.com Suite 1200, Mail Stop 30/12B2

Phone: +1 (703) 284-4641 1300 Seventeenth Street North

Fax: +1 (703) 284-2766 Arlington, VA 22209-3801 USA

8. Full Copyright Statement

This document and translations of it may be copied and furnished to

others, and derivative works that comment on or otherwise explain it

or assist in its implementation may be prepared, copied, published

and distributed, in whole or in part, without restriction of any

kind, provided that the above copyright notice and this paragraph are

included on all such copies and derivative works. However, this

document itself may not be modified in any way, such as by removing

the copyright notice or references to the Internet Society or other

Internet organizations, except as needed for the purpose of

developing Internet standards in which case the procedures for

copyrights defined in the Internet Standards process must be

followed, or as required to translate it into languages other than

English.

The limited permissions granted above are perpetual and will not be

revoked by the Internet Society or its successors or assigns.

This document and the information contained herein is provided on an

"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING

TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING

BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION

HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF

MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

Funding for the RFCEditor function is currently provided by the

Internet Society.