Network Working Group V. Smyslov
Request for Comments: 2628 TWS
Category: Informational June 1999
Simple Cryptographic Program Interface (Crypto API)
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.
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
Abstract
This document describes a simple Application Program Interface to
cryptographic functions. The main purpose of sUCh an interface is to
separate cryptographic libraries from internet applications, thus
allowing an independent development of both. It can be used in
various internet applications such as [IPsec], [ISAKMP], [IKE],
[TLS].
Table of Contents
1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3. Objectives of Development . . . . . . . . . . . . . . . . . . 3
2. Cryptoplugin Structure. . . . . . . . . . . . . . . . . . . . . 3
3. Program Interface . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Cryptoplugin Initialization Function. . . . . . . . . . . . . 4
3.1.1. Description of CryptoPluginInfo structure . . . . . . . . . 6
3.1.2. Description of CryptoAlgInfo structure. . . . . . . . . . . 6
3.2. Cryptoplugin Deinitialization Function. . . . . . . . . . . . 9
3.3. Cryptographic Context Opening Function. . . . . . . . . . . . 10
3.4. Cryptographic Context Reopening Function. . . . . . . . . . . 11
3.5. Cryptographic Context Closing Function. . . . . . . . . . . . 12
3.6. Key Verification Function . . . . . . . . . . . . . . . . . . 12
3.7. Data Transformation Function. . . . . . . . . . . . . . . . . 13
3.7.1. For CRYPTO_TYPE_ENCRYPT Algorithm Type. . . . . . . . . . . 13
3.7.2. For CRYPTO_TYPE_DECRYPT Algorithm Type. . . . . . . . . . . 14
3.7.3. For CRYPTO_TYPE_SIGN Algorithm Type . . . . . . . . . . . . 15
3.7.4. For CRYPTO_TYPE_VERIFY Algorithm Type . . . . . . . . . . . 17
3.7.5. For CRYPTO_TYPE_COMPRESS Algorithm Type . . . . . . . . . . 18
3.7.6. For CRYPTO_TYPE_UNCOMPRESS Algorithm Type . . . . . . . . . 18
3.7.7. For CRYPTO_TYPE_HASH Algorithm Type . . . . . . . . . . . . 19
3.7.8. For CRYPTO_TYPE_RANDOM Algorithm Type. . . . . . . . . . . 21
3.8. Cryptographic Context Control Function. . . . . . . . . . . . 22
4. Cryptoplugin Registration Procedure . . . . . . . . . . . . . . 23
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 23
6. References. . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 24
Appendix A. The interface specification as a C header file . . . . 25
Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 30
1. Introduction
1.1. Summary
Nowadays internet applications that require cryptographic functions
at the level of operating system kernel, use the method that assumes
the libraries must be compiled/linked together with the module
(driver) which provides product functionality. For the sake of
possibility of independent development of the cryptographic modules
and in order to provide a simple, effective and universal (suitable
for application and as well kernel level of operating system)
solution this specification offers the method to extract encrypting
algorithms to the separate cryptographic modules.
This document describes simple open interface (Crypto API) to
external cryptographic libraries optimized both for the application
and kernel level of the operating system.
1.2. Terminology
Cryptoplugin
Operation system unit (driver, shared library, module) that
provides cryptographic functions via well-defined (but OS-
specific) interface.
Cryptolibrary
Part of cryptoplugin that provides its cryptographic functionality
via Crypto API.
Wrapper
Part of cryptoplugin that provides interfaces translation between
Crypto API and OS-specific interface.
Definition of all cryptography related terms can be found in
[Schneier].
1.3. Objectives of Development
The objectives of Simple CryptoAPI development are as follows:
1) To extract program implementations of encryption, one-way hash
function, digital signature and random numbers generation
algorithms to separate, independently developed modules.
2) To provide version independence between using encryption
modules and external cryptoplugin.
3) To ensure platform independent developments of encrypting
algorithm modules with portable source code.
4) To enable independent development of modules and compatibility
of modules developed independently.
2. Cryptoplugin Structure
In order to provide fast exchange between the cryptoplugin and its
client the cryptoplugin is implemented as a separate driver (or
module) of the particular operating system (Fig.1). Cryptoplugin
consists of two parts (Fig.2):
1) cryptolibrary itself (1)
2) system-dependent module (wrapper) for interaction between
cryptolibrary and its client (2)
Cryptoplugin initialization
/ by the operating system
+------------------+ +--+-------------+
Cryptoplugin's ------->
Cryptoplugin
client <-------
+------------------+ +---+-------------+
\ System-dependent CPI
Fig. 1 Interaction between cryptoplugin and its client
+---------------+-------------------------------+
--> Submodule of
Submodule -
encrypting algorithms (1)
wrapper (2)
<-- (cryptolibrary)
+---------------+-------------------------------+
\ Cryptographic Program Interface
Fig. 2 Cryptoplugin structure
The system-dependent module (wrapper) is delivered by the driver-
client developer in the form of source code or in the form of
libraries (for example, in the form of object files) for particular
operating system. The wrapper is intended for translation of
system-independent application interface to the particular system-
dependent interface with the cryptoplugin's client. The wrapper
context does not include components specific to cryptoplugin's client
functionality or to some cryptographic algorithm. The interface
described in section 3 is the standard for interaction between the
submodules (1) and (2).
A cryptoplugin can contain a number of different algorithms.
Moreover, it can contain some different implementations of one
particular algorithm.
3. Program Interface
The CPI (Cryptographic Program Interface) consists of a set of
functions eXPorted by encrypting algorithm submodule (cryptolibrary).
The interface functions are described below (see also Appendix A).
3.1. Cryptoplugin Initialization Function
The function is intended for cryptoplugin initialization and
oBTaining information about algorithms contained in cryptoplugin. The
function is called once before the beginning of cryptoplugin
operation.
/* CryptoPlugin initialization. Returns pointer to CryptoPluginInfo
structure on success or NULL on fatal error. */
CryptoPluginInfo *CryptoPluginInit(
void *param);/* Ptr to OS parameters
(platform-specific) */
Description of parameters:
param - pointer to system-dependent parameters transmitted to
cryptoplugin by the operating system. Intention and format of
parameters are specific to each operating system and should be
described in documentation on the cryptoplugin wrapper.
The function is called at the moment of cryptoplugin initialization.
If succeeded it returns the pointer to CryptoPluginInfo structure
that describes the module and algorithms implemented in the
cryptolibrary. If function call did not succeed, function will
return NULL or appropriate error code in CryptoPluginInfo structure
status field. If the initialization is partially succeeded then the
cryptoplugin either returns CryptoPluginInfo structure transformed so
that it contains only successfully initialized algorithms or returns
appropriate error code in status field of CryptoAlgInfo structures
that describes the reason for the failure.
Error codes for the function:
NULL - fatal unsuccessful cryptoplugin initialization. The module
is unable even to indicate the reason of failure.
The pointer to cryptoplugin description structure in the case of full
or partial success. The status fields in CryptoPluginInfo structure
and in comprised CryptoAlgInfo structures can be set to the following
values:
CRYPTO_OK - cryptoplugin (algorithm) is initialized successfully.
CRYPTO_ERR_GENERAL - internal error.
CRYPTO_ERR_NOT_SUPPORTED - (only for algorithm) - the algorithm
is not supported by the module at the moment.
CRYPTO_ERR_HARDWARE - error of hardware initialization.
CRYPTO_ERR_NO_RESOURCES - insufficient internal resources.
CRYPTO_ERR_NO_MEMORY - not enough memory. Contrary to general
CRYPTO_ERR_NO_RESOURCES error this code assumes that the
calling module can release system memory (if it is in position
to) and try to call the function once again.
3.1.1. Description of CryptoPluginInfo structure
The CryptoPluginInfo structure consists of header of fixed size that
generally describes cryptoplugin and array of CryptoAlgInfo
structures following the header. Each structure describes particular
algorithm implemented in the cryptolibrary (see Appendix A)
Structure fields description:
cpi_version - CPI version (should be CRYPTO_VER (1,0)). CPI
version determines both functions set and fields layout in
CryptoPluginInfo/CryptoAlgInfo structures.
status - returns the error code if cryptoplugin initialization
failed (otherwise should be CRYPTO_OK)
name - text cryptoplugin description (ASCII-7 characters only; all
unused bytes must be set to 0).
version - cryptoplugin version (CRYPTO_VER(maj,min)).
flags - various flags that characterize the cryptoplugin.
number_of_algs - number of algorithms the cryptolibrary comprises
of (i.e. the number of consequent CryptoAlgInfo structures).
3.1.2. Description of CryptoAlgInfo structure
Structure fields description
status - returns the error code if particular algorithm
initialization failed (otherwise should be CRYPTO_OK).
id - algorithm identifier (CRYPTO_A_XXX). Values in the range of
0..249 are reserved; Values in the range of 250..32767 indicate
algorithms not enrolled in standard list. It should be
emphasized that algorithm IDs are independent for each
algorithm type. But it is considered that pairs of types
CRYPTO_TYPE_ENCRYPT and CRYPTO_TYPE_DECRYPT, CRYPTO_TYPE_SIGN
and CRYPTO_TYPE_VERIFY, CRYPTO_TYPE_COMPRESS and
CRYPTO_TYPE_UNCOMPRESS are equivalent because they define
reverse actions of the same nature.
group - algorithm implementation group (variants algorithm
implementations with various parameters not covered by
CryptoAlgInfo structure). Values in the range of 0..32767 are
well-known numbers defined in Appendix A; vendors may
arbitrarily use values in the range of 32768..65535.
type - algorithm type (CRYPTO_TYPE_XXX). Unambiguously determines
algorithm application.
version - version of algorithm implementation (CRYPTO_VER
(maj,min)).
flags - flags that characterize the algorithm and its
implementation. All bits, that are not defined in Appendix A,
must be zeroed.
maxcontexts - maximum cryptographic contexts number that are
simultaneously supported by the algorithm implementation (0 if
the number is unlimited or is limited only by environmental
conditions like memory size).
name - text algorithm name (ASCII characters use only; all unused
bytes must be set to 0).
The next information depends on algorithm type:
For encryption algorithms (CRYPTO_TYPE_ENCRYPT and
CRYPTO_TYPE_DECRYPT):
blocklen - data block length in bytes (value 1 must be used for
stream cipher algorithms).
keylen - encrypting (or decrypting) key length in bytes.
outlen - output data size for conversion of one input data block
in bytes. Usually it is equal to blocklen. When prediction of
this value is impossible zero value must be indicated.
milen - size of initialization vector (for block algorithms) or
message indicator (for stream algorithms) in bytes. For block
algorithms zero value of the parameter means that the algorithm
implements ECB encoding. Non-zero milen parameter means that
the algorithm implements CBC encoding. For stream algorithms
zero value of the parameter means that the message indicator is
not required.
For signature algorithms (CRYPTO_TYPE_SIGN):
blocklen - block size in bytes. The length of input signature data
will be padded up to this value. When there is no need in
padding the value of 1 must be set.
keylen - private key length in bytes.
outlen - signature length in bytes. When prediction of this value
is impossible 0 value must be indicated. If the signature
consists of several values then the total length is indicated.
milen - non-zero value specifies signature parameter length
(random number), zero value indicates that the parameter is not
required.
For signature verification algorithms (CRYPTO_TYPE_VERIFY):
blocklen - is not used.
keylen - length of public key in bytes.
outlen - signature length in bytes. When prediction of this value
is impossible 0 value must be indicated. If the signature
consists of several values then the total length is indicated.
milen - is not used.
For data compression algorithms (CRYPTO_TYPE_COMPRESS):
blocklen - see outlen.
keylen - is not used.
outlen - if the algorithm provides the fixed compression with
known value then it is indicated as blocklen/outlen ratio. The
values can be arbitrary. If the compression value is not known
then outlen is set to 0 and blocklen is not used.
milen - is not used.
For data uncompressing algorithms (CRYPTO_TYPE_UNCOMPRESS):
blocklen - see outlen.
keylen - is not used.
outlen - if the algorithm provides the fixed compression with
known value then it is indicated as blocklen/outlen ratio. The
values can be arbitrary. It is natural that the ratio will be
reverse to the similar value for the same algorithm but of
CRYPTO_TYPE_COMPRESS type. If the compression value is not
known then outlen is set to 0 and blocklen is not used.
milen - is not used.
For one-way hash function algorithms (CRYPTO_TYPE_HASH):
blocklen - block size in bytes. The length of input data will be
padded up to this value. When there is no need in padding value
1 should be used.
keylen - is not used.
outlen - resulting hash value length in bytes.
milen - is not used.
For random number generation algorithms (CRYPTO_TYPE_RANDOM):
blocklen - is not used.
keylen - initial seed length (0 - if not required, for example in
a physical effects based generators).
outlen - resulting random number length in bytes (0 - arbitrary)
milen - is not used.
3.2. Cryptoplugin Deinitialization Function
/* Plugin deinitialization */
CRYPTO_STATUS CryptoPluginFini(void);
The function is called before the cryptoplugin operation is to be
terminated. Function execution causes closing of all open
cryptographic contexts, system resources deallocation and hardware
deinitialization. The value returned is informational only.
Return codes for the function:
CRYPTO_OK - cryptoplugin is deinitialized successfully.
CRYPTO_ERR_GENERAL - internal error.
CRYPTO_ERR_UNCLOSED_HANDLES - warning that there were open
cryptographic contexts during cryptoplugin deinitialization.
The warning is informational only. The open contexts are
destroyed anyway.
3.3. Cryptographic Context Opening Function
New algorithm instance (cipher state) */
CRYPTO_STATUS CryptoOpen(
CRYPTO_HANDLE *state, /* Pointer to cipher state
handle (filled on exit) */
long algnum, /* Algorithm number in
CryptoPluginInfo structure */
const char *key); /* key (in plain) */
The function creates cryptographic context copy inside cryptoplugin
and initializes it with the provided key. Later the handle of the
context is used in calls of other algorithm functions.
Description of parameters:
state - pointer to the variable that will be set to the handle of
the context created if succeeded. NULL parameter value should
result in the CRYPTO_ERR_BAD_PARAMS code returned by the
function.
algnum - algorithm number in the cryptoplugin. It is equal to the
number of CryptoAlgInfo structure (that describes the
algorithm) in CryptoPluginInfo structure. The number begins
with zero value. It should be taken into account that it is not
an algorithm identifier but its number in the cryptoplugin.
key - pointer to the key (if it is required) or to the seed (for
random number generation algorithm).
Notes.
1. Generated cryptographic context is stored inside the cryptoplugin
until it will be destroyed by the CryptoAlgClose function call.
The maximum number of cryptographic contexts supported by
cryptoplugin can be indicated in algorithm parameters description.
If maximum number of cryptographic contexts equals to zero then
the cryptographic contexts number is either unlimited (for
example, for stateless algorithms like random number generators
and one-way hash functions) or it is limited by external factors
only (like memory size).
Return codes for the function:
CRYPTO_OK - successful completion.
CRYPTO_ERR_GENERAL - internal error.
CRYPTO_ERR_NO_RESOURCES - insufficient internal resources.
CRYPTO_ERR_NO_MEMORY - not enough memory. Contrary to general
CRYPTO_ERR_NO_RESOURCES error this code assumes that the
calling module can release system memory (if it is in
position to) and try to call the function once again.
CRYPTO_ERR_BAD_PARAMS - invalid parameters (invalid algorithm
number, zero pointer to the handle or to key (seed) if it is
required.
3.4. Cryptographic Context Reopening Function
/* Reinitialize algorithm instance */
CRYPTO_STATUS CryptoReOpen(
CRYPTO_HANDLE state, /* current cipher state handle */
const char *key); /* key (in plain) */
The function reinitializes an existing context. This function is used
for key change without new system resources allocation. The function
parameters are handle of opened earlier context and pointer to a new
key.
Return codes for the function:
CRYPTO_OK - successful completion.
CRYPTO_ERR_GENERAL - internal error.
CRYPTO_ERR_BAD_HANDLE - invalid cryptographic context handle.
CRYPTO_ERR_NO_RESOURCES - insufficient internal resources.
CRYPTO_ERR_NO_MEMORY - not enough memory. Contrary to general
CRYPTO_ERR_NO_RESOURCES error this code assumes that the
calling module may release system memory and try function
call once more.
CRYPTO_ERR_BAD_PARAMS - invalid parameters (invalid algorithm
number, zero pointer to the handle or to key (seed) if it is
required.
3.5. Cryptographic Context Closing Function
/* Destroy algorithm instance */
CRYPTO_STATUS CryptoClose(
CRYPTO_HANDLE state); /* Handle of cipher state */
The function provides cryptographic context destruction. The
cryptographic context handle is its parameter. The value returned is
informational only.
Return codes for the function:
CRYPTO_OK - successful completion.
CRYPTO_ERR_GENERAL - internal error.
CRYPTO_ERR_BAD_HANDLE - invalid cryptographic context handle.
3.6. Key Verification Function
/* Check key for possible weakness */
CRYPTO_STATUS CryptoCheckForWeakKey(
long algnum, /* Algorithm number in
CryptoPluginInfo structure */
const char *key); /* Proposed key */
The function verifies key material whether it is weak (from the
algorithm's point of view). The function is actual for
encryption/decryption or signing/verification algorithms only.
Algorithm number (similar to CryptoAlgOpen) and pointer to the key to
be verified are the parameters.
Return codes for the function:
CRYPTO_O - the key has passed the test.
CRYPTO_ERR_WEAK_KEY - the key has not passed the test (being weak
or possibly weak).
CRYPTO_ERR_NOT_SUPPORTED - is not supported.
CRYPTO_ERR_NO_RESOURCES - insufficient internal resources.
CRYPTO_ERR_NO_MEMORY - not enough memory. Contrary to general
CRYPTO_ERR_NO_RESOURCES error this code assumes that the
calling module can release system memory (if it is in
position to) and try to call the function once again.
3.7. Data Transformation Function
/* Perform CryptoTransform (depends on cipher state type) */
CRYPTO_STATUS CryptoTransform(
CRYPTO_HANDLE state, /* Cipher state */
const char *inbuff,/* input data */
long inlen, /* input data length */
char *outbuff,/* output buffer */
long *outlen,/* On entry - output buffer
length, on exit - number of
bytes written to outbuff */
char *mi); /* Message indicator */
This is a cryptographic data transformation function. Function call
results and function parameters are dependent on algorithm type. For
algorithm types CRYTO_TYPE_ENCRYPT, CRYPTO_TYPE_DECRYPT,
CRYPTO_TYPE_SIGN and CRYPTO_TYPE_VERIFY (items 3.7.1 - 3.7.4)
function call results are history independent.
Note. Stream encryption algorithms may seem an "exception". However
the same cryptoalgorithm handle must hide its history dependence. For
algorithm types CRYPTO_TYPE_COMPRESS, CRYPTO_TYPE_UNCOMPRESS and
CRYPTO_TYPE_HASH (items 3.7.5 - 3.7.7) function calls are history
dependent. For the CRYPTO_TYPE_RANDOM algorithm function call may be
for different implementations either dependent or independent on the
history.
3.7.1. For CRYPTO_TYPE_ENCRYPT Algorithm Type:
The function encrypts input data. Its parameters are intended for:
inbuff - pointer to the input data. If this parameter is equal to
NULL then the function should return the
CRYPTO_ERR_BAD_PARAMS error code.
inlen - input data size (in bytes). If the size indicated in
algorithm description is divisible by blocklen then
padding is not carried out. Otherwise the algorithm
either caries out padding according to the algorithm
standard or returns appropriate error code
(CRYPTO_ERR_BAD_PARAMS). The zero parameter is allowed so
that the function quits at once and returns CRYPTO_OK
code.
outbuff - output data buffer. NULL parameter value results in the
outlen parameter setting to output buffer size required
to encrypt the input buffer represented. In this case the
CRYPTO_ERR_SMALL_BUFFER error should not be returned.
outlen - Output buffer size is an input function parameter while
the number of bytes written in the output buffer is the
output parameter. Both the NULL parameter value and the
zero value addressed result in CRYPTO_ERR_BAD_PARAMS code
returned by the function.
mi - message indicator. Its content depends on whether the
block or stream algorithm is applied. In the block
algorithm case it is set to the last block encrypted.
When the first block is encrypted mi parameter specifies
initial initialization vector. In the stream algorithm
case it is set to the offset of the first byte encrypted
in the stream. If the algorithm uses the message
indicator and the mi parameter value is set to NULL then
function should return CRYPTO_ERR_BAD_PARAMS. If the
algorithm (ECB Mode encrypting as an example) does not
apply the message indicator then NULL value of mi is
acceptable while non-NULL value should be ignored.
Returned values:
CRYPTO_OK - successful completion.
CRYPTO_ERR_GENERAL - internal error.
CRYPTO_ERR_BAD_HANDLE - invalid cryptographic context handle.
CRYPTO_ERR_NO_RESOURCES - insufficient internal resources.
CRYPTO_ERR_NO_MEMORY - not enough memory. Contrary to general
CRYPTO_ERR_NO_RESOURCES error this code assumes that the
calling module can release system memory (if it is in
position to) and try to call the function once again.
CRYPTO_ERR_SMALL_BUFFER - insufficient output buffer size.
CRYPTO_ERR_BAD_PARAMS - invalid parameters.
3.7.2. For CRYPTO_TYPE_DECRYPT Algorithm Type:
The function decrypts the input data. Its parameters are intended for:
inbuff - pointer to the input data. If the parameter is equal to
NULL then the function should return the
CRYPTO_ERR_BAD_PARAMS error code.
inlen - input data size (in bytes). When the parameter is set to
zero the function quits at once and CRYPTO_OK code is returned.
outbuff - output data buffer. NULL parameter value results in the
outlen parameter setting to output buffer size required
to decrypt the input buffer represented. In this case the
CRYPTO_ERR_SMALL_BUFFER error should not be returned.
outlen - Output buffer size is an input function parameter while
the number of bytes written in the output buffer is the
output parameter. Both the NULL parameter value and the
zero value addressed result in CRYPTO_ERR_BAD_PARAMS code
returned by the function.
mi - message indicator. The content depends on whether the
block or stream algorithm is applied. In the block
algorithm case it is set to the last block encrypted.
When the first block is decrypted mi specifies initial
initialization vector. In the stream algorithm case it is
set to the offset of the first byte decrypted in the
stream. If the algorithm uses the message indicator and
the mi parameter is set to NULL then function should
return CRYPTO_ERR_BAD_PARAMS. If the algorithm (ECB Mode
as an example) does not apply the message indicator then
NULL value of mi is acceptable while non-NULL value
should be ignored.
Returned values:
CRYPTO_OK - successful completion.
CRYPTO_ERR_GENERAL - internal error.
CRYPTO_ERR_BAD_HANDLE - invalid cryptographic context handle.
CRYPTO_ERR_NO_RESOURCES - insufficient internal resources.
CRYPTO_ERR_NO_MEMORY - not enough memory. Contrary to general
CRYPTO_ERR_NO_RESOURCES error this code assumes that the
calling module can release system memory (if it is in
position to) and try to call the function once again.
CRYPTO_ERR_SMALL_BUFFER - insufficient output buffer size.
CRYPTO_ERR_BAD_PARAMS - invalid parameters.
3.7.3. For CRYPTO_TYPE_SIGN Type Algorithm:
The function signs the input data. Its parameters are intended for:
inbuff - pointer to the input data. If the parameter is equal to
NULL then the function should return the
CRYPTO_ERR_BAD_PARAMS code error.
inlen - input data size (in bytes). If the size indicated in
algorithm description is divisible by blocklen then
padding is not carried out. Otherwise the algorithm
either caries out padding according to the algorithm
standard or returns appropriate error code
(CRYPTO_ERR_BAD_PARAMS). The zero parameter is allowed so
that the function quits at once and returns CRYPTO_OK
code.
outbuff - output data buffer. NULL parameter value results in the
outlen parameter setting to output buffer size required
to sign the input buffer represented. In this case the
CRYPTO_ERR_SMALL_BUFFER error should not be returned.
outlen - Output buffer size is an input function parameter while
the number of bytes written in the output buffer is the
output parameter. Both the NULL parameter value and the
zero value addressed result in CRYPTO_ERR_BAD_PARAMS code
returned by the function.
mi - pointer to signature parameter (random number usually) if
milen parameter in algorithm description is non-zero. In
this case zero mi parameter indicates that the parameter
should be chosen (generated) inside the algorithm. If
milen parameter in algorithm description is set to zero
then mi parameter is ignored.
Returned values:
CRYPTO_OK - successful completion.
CRYPTO_ERR_GENERAL - internal error.
CRYPTO_ERR_BAD_HANDLE - invalid cryptographic context handle.
CRYPTO_ERR_NO_RESOURCES - insufficient internal resources.
CRYPTO_ERR_NO_MEMORY - not enough memory. Contrary to general
CRYPTO_ERR_NO_RESOURCES error this code assumes that the
calling module can release system memory (if it is in
position to) and try to call the function once again.
CRYPTO_ERR_SMALL_BUFFER - insufficient output buffer size.
CRYPTO_ERR_BAD_PARAMS - invalid parameters.
3.7.4. For CRYPTO_TYPE_VERIFY Algorithm Type:
The function verifies input data signature. Its parameters are
intended for:
inbuff - pointer to the input data. If the parameter is equal to
NULL then the function should return the CRYPTO_ERR_BAD_PARAMS
code error.
inlen - input data size (in bytes). The zero parameter is allowed
so that the function quits at once and returns CRYPTO_OK code.
outbuff -pointer to the signature. If the parameter is set to NULL
then the function returns CRYPTO_ERR_BAD_PARAMS error code. If
the signature consists of several parts then they are combined
to one array.
outlen - specifies the signature length if the signature length is
set to zero in algorithm description structure. If non-zero
value is specified in algorithm description structure then the
parameter is ignored. If the signature consists of several
parts then the maximum part length multiplied by the number of
parts is specified.
mi - is not used.
Returned values:
CRYPTO_OK - successful completion.
CRYPTO_ERR_INVALID_SIGNATURE - invalid signature.
CRYPTO_ERR_GENERAL - internal error.
CRYPTO_ERR_BAD_HANDLE - invalid cryptographic context handle.
CRYPTO_ERR_NO_RESOURCES - insufficient internal resources.
CRYPTO_ERR_NO_MEMORY - not enough memory. Contrary to general
CRYPTO_ERR_NO_RESOURCES error this code assumes that the
calling module can release system memory (if it is in
position to) and try to call the function once again.
CRYPTO_ERR_SMALL_BUFFER - insufficient output buffer size.
CRYPTO_ERR_BAD_PARAMS - invalid parameters.
3.7.5. For CRYPTO_TYPE_COMPRESS Algorithm Type:
The function compresses the input data. Its parameters are intended
for:
inbuff - pointer to the input data.
inlen - input data size (in bytes). The zero parameter is allowed
so that the function quits at once and returns CRYPTO_OK code.
outbuff - output data buffer. NULL parameter value results in the
outlen parameter setting to output buffer size required to
compress the input buffer represented. In this case the
CRYPTO_ERR_SMALL_BUFFER error should not be returned.
outlen - Output buffer size is an input function parameter while
the number of bytes written in the output buffer is the output
parameter. Both the NULL parameter value and the zero value
addressed result in CRYPTO_ERR_BAD_PARAMS code returned by the
function.
mi - is not used.
Returned values:
CRYPTO_OK - successful completion.
CRYPTO_ERR_GENERAL - internal error.
CRYPTO_ERR_BAD_HANDLE - invalid cryptographic context handle.
CRYPTO_ERR_NO_RESOURCES - insufficient internal resources
CRYPTO_ERR_NO_MEMORY - not enough memory. Contrary to general
CRYPTO_ERR_NO_RESOURCES error this code assumes that the
calling module can release system memory (if it is in
position to) and try to call the function once again.
CRYPTO_ERR_SMALL_BUFFER - insufficient output buffer size.
CRYPTO_ERR_BAD_PARAMS - invalid parameters.
3.7.6. For CRYPTO_TYPE_UNCOMPRESS Algorithm Type:
The function decompresses the input data. Its parameters are
intended for:
inbuff - pointer to the input data.
inlen - input data size (in bytes). The zero parameter is allowed
so that the function quits at once and returns CRYPTO_OK code.
outbuff - output data buffer. NULL parameter value results in the
outlen parameter setting to output buffer size required to
decompress the input buffer represented. In this case the
CRYPTO_ERR_SMALL_BUFFER error should not be returned.
outlen - Output buffer size is an input function parameter while
the number of bytes written in the output buffer is the output
parameter. Both the NULL parameter value and the zero value
addressed result in CRYPTO_ERR_BAD_PARAMS code returned by the
function.
mi - is not used.
Returned values:
CRYPTO_OK - successful completion.
CRYPTO_ERR_GENERAL - internal error.
CRYPTO_ERR_BAD_HANDLE - invalid cryptographic context handle.
CRYPTO_ERR_NO_RESOURCES - insufficient internal resources.
CRYPTO_ERR_NO_MEMORY - not enough memory. Contrary to general
CRYPTO_ERR_NO_RESOURCES error this code assumes that the
calling module can release system memory (if it is in
position to) and try to call the function once again.
CRYPTO_ERR_SMALL_BUFFER - insufficient output buffer size.
CRYPTO_ERR_BAD_PARAMS - invalid parameters.
3.7.7. For CRYPTO_TYPE_HASH Algorithm Type:
The function calculates the hash value of the input data. Its
parameters are intended for:
inbuff - pointer to the input data. If the parameter is of NULL
value then the function calculates cumulative hash value for
the data represented (taking into account all previous data
represented). If total length of all the data represented by
the moment is divisible by blocklen and outbuff is non-NULL
then it is returned to outbuff. Nothing is written in outbuff
when the length is not divisible by blocklen. NULL inbuff
indicates the last conversion when the input data is padded up
to the blocklen size and the result is written to outbuff
address. The padding procedure is defined for the algorithm.
inlen - input data size (in bytes). The zero parameter is allowed
when the function quits at once and returns CRYPTO_OK code.
outbuff - output data buffer.
outlen - Output buffer size is an input function parameter while
the number of bytes written in the output buffer is the output
parameter. If intermediate conversion value (inbuff is not
NULL) and total length of data represented by the moment are
not divisible by blocklen then outlen is set to zero and the
hash value is not written in outbuff. Both the NULL parameter
value and the zero value addressed result in
CRYPTO_ERR_BAD_PARAMS code returned by the function.
mi - is not used.
Returned values:
CRYPTO_OK - successful completion.
CRYPTO_ERR_GENERAL - internal error.
CRYPTO_ERR_BAD_HANDLE - invalid cryptographic context handle.
CRYPTO_ERR_NO_RESOURCES - insufficient internal resources.
CRYPTO_ERR_NO_MEMORY - not enough memory. Contrary to general
CRYPTO_ERR_NO_RESOURCES error this code assumes that the
calling module can release system memory (if it is in position
to) and try to call the function once again.
CRYPTO_ERR_SMALL_BUFFER - insufficient output buffer size.
CRYPTO_ERR_BAD_PARAMS - invalid parameters.
3.7.8. For CRYPTO_TYPE_RANDOM Algorithm Type:
The function generates a random number. Its parameters are intended
for:
inbuff - pointer to the input data used for generation (when one
of the pseudorandom algorithms is implemented). NULL parameter
indicates absence of the input data.
inlen - input data size (in bytes).
outbuff - output data
outlen - Output buffer size is an input function parameter while
the number of bytes written in the output buffer is the output
parameter. If zero (i.e. arbitrary) generated number size is
set in the algorithm description then the outlen value
determines the number of random bytes required by the calling
procedure.
mi - is not used.
Returned values:
CRYPTO_OK - successful completion.
CRYPTO_ERR_GENERAL - internal error.
CRYPTO_ERR_BAD_HANDLE - invalid cryptographic context handle.
CRYPTO_ERR_NO_RESOURCES - insufficient internal resources.
CRYPTO_ERR_NO_MEMORY - not enough memory. Contrary to general
CRYPTO_ERR_NO_RESOURCES error this code assumes that the
calling module can release system memory (if it is in
position to) and try to call the function once again.
CRYPTO_ERR_SMALL_BUFFER - insufficient output buffer size.
CRYPTO_ERR_BAD_PARAMS - invalid parameters.
3.8. Cryptographic Context Control Function
/* Algorithm control */
CRYPTO_STATUS CryptoControl(
CRYPTO_HANDLE state, /* Cipher state handle */
long cmd, /* Control command */
long param, /* Parameter id */
char val, /* Parameter value */
long *len); /* For CRYPTO_GET: on entry -
val buffer length, on exit -
number of bytes written to
val; for CRYPTO_SET: length
of value to set */
The function provides cryptographic context internal parameters
management. It may be used to check context parameters or to change
the context state, for example it may return information about
cryptoalgorithm (is given context uses hardware encryption
facilities), or it may "scroll" stream algorithms context if
necessary, etc.
Description of parameters:
state - cryptographic context handle.
cmd - command (CRYPTO_GET or CRYPTO_SET).
param - identifier of parameter. Values in the range of 0..32767
are assigned well-known numbers for all algorithms.
Values in the range of 32768..65535 mean various
variables for various algorithms (may be arbitrarily used
by cryptolibrary developer).
val - pointer to the data buffer.
len - data size (in bytes).
Returned values:
CRYPTO_OK - successful completion.
CRYPTO_ERR_GENERAL - internal error.
CRYPTO_ERR_BAD_HANDLE - invalid cryptographic context handle.
CRYPTO_ERR_NO_RESOURCES - insufficient internal resources.
CRYPTO_ERR_NO_MEMORY - not enough memory. Contrary to general
CRYPTO_ERR_NO_RESOURCES error this code assumes that the
calling module can release system memory (if it is in
position to) and try to call the function once again.
CRYPTO_ERR_SMALL_BUFFER - insufficient output buffer size.
CRYPTO_ERR_BAD_PARAMS - invalid parameters.
4. Cryptoplugin Registration Procedure
Cryptoplugin should be linked together with the cryptoplugin wrapper
library delivered by the cryptoplugin's client developer according to
the rules specified by the module-client developer for each platform.
It should result in a driver (module) of appropriate operating system
that implements the cryptolibrary functions. The driver should be one
of the drivers loaded during operating system boot. The procedure of
cryptoplugin driver installation should be defined, documented, and
automated when necessary, by the cryptoplugin developer. At the
beginning of operation the driver-client determines cryptoplugin
driver availability and establishes interconnection with it. Both
module-client configuration and current security policy determine
data conversion algorithms to be chosen.
5. Security Considerations
Security issues are addressed throughout this memo.
6. References
[Schneier] Bruce Schneier, Applied Cryptography - Protocols,
Algorithms, and Source Code in C (Second Edition), John
Wiley & Sons, Inc., 1996.
[IPsec] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC2401, November 1998.
[ISAKMP] Maughhan, D., Schertler, M. Schneider, M. and J. Turner,
"Internet Security Association and Key Management Protocol
(ISAKMP)", RFC2408, November 1998.
[IKE] Harkins, D. and D. Carrel, "The Internet Key Exchange
(IKE)", RFC2409, November 1998.
[TLS] Dierks, T. and C. Allen, "The TLS protocol Version 1.0",
RFC2246, January 1999.
7. Author's Address
Valery Smyslov
TWS
Centralny prospekt, 11,
Moscow, Russia
Phone: +7 (095) 531 4633
Fax: +7 (095) 531 2403
EMail: svan@trustworks.com
Appendix A. The interface specification as a C header file
#ifndef __CRYPTPI_H
#define __CRYPTPI_H
#define CRYPTO_VER(maj,min) (((maj & 0xff) << 8) (min & 0xff))
#define CRYPTO_MAJ_VER(ver) ((ver >> 8) & 0xff)
#define CRYPTO_MIN_VER(ver) (ver & 0xff)
#define CRYPTO_PLUGIN_NAME_LEN 64 /* Must be multiple of 4 to */
#define CRYPTO_ALG_NAME_LEN 32 /* avoid alignment problems */
#ifndef CRYPTO_HANDLE
#define CRYPTO_HANDLE void* /* cipher state handle */
#endif
typedef enum tag_CRYPTO_STATUS {
CRYPTO_OK = 1, /* success */
CRYPTO_ERR_GENERAL, /* undefined (internal) error */
CRYPTO_ERR_NOT_SUPPORTED, /* unsupported */
CRYPTO_ERR_BAD_HANDLE, /* invalid handle */
CRYPTO_ERR_SMALL_BUFFER, /* insufficient output buffer
size */
CRYPTO_ERR_WEAK_KEY, /* key is considered to be weak
(semiweak, pseudoweak) */
CRYPTO_ERR_NO_RESOURCES, /* insufficient resources to
perform operation */
CRYPTO_ERR_NO_MEMORY, /* insufficient memory to
perform operation */
CRYPTO_ERR_BAD_PARAMS, /* invalid parameters */
CRYPTO_ERR_HARDWARE, /* hardware error */
CRYPTO_ERR_INVALID_SIGNATURE, /* invalid signature */
CRYPTO_ERR_UNCLOSED_HANDLES /* unclosed handles exist while
plugin deinitializises */
} CRYPTO_STATUS;
/* CryptoControl commands */
#define CRYPTO_GET 1 /* get parameter */
#define CRYPTO_SET 2 /* set parameter */
/* Currently defined algorithm types */
#define CRYPTO_TYPE_ENCRYPT 1
#define CRYPTO_TYPE_DECRYPT 2
#define CRYPTO_TYPE_SIGN 3
#define CRYPTO_TYPE_VERIFY 4
#define CRYPTO_TYPE_COMPRESS 5
#define CRYPTO_TYPE_UNCOMPRESS 6
#define CRYPTO_TYPE_HASH 7
#define CRYPTO_TYPE_RANDOM 8
/* Currently defined algorithm IDs (for types
CRYPTO_TYPE_ENCRYPT & CRYPTO_TYPE_DECRYPT) */
#define CRYPTO_AE_DUMMY 1 /* no encryption */
#define CRYPTO_AE_DES 2 /* DES-CBC */
#define CRYPTO_AE_3DES_EDE 3 /* Triple DES-EDE-CBC */
#define CRYPTO_AE_IDEA 4 /* IDEA-CBC */
#define CRYPTO_AE_RC2 5 /* RC2 */
#define CRYPTO_AE_RC4 6 /* RC4 */
#define CRYPTO_AE_RC5 7 /* RC5 */
#define CRYPTO_AE_SAFER 8 /* SAFER */
#define CRYPTO_AE_CAST 9 /* CAST */
#define CRYPTO_AE_BLOWFISH 10 /* Blowfish */
#define CRYPTO_AE_RSA 11 /* RSA */
#define CRYPTO_AE_GOST 12 /* GOST */
/* Currently defined algorithm IDs (for types
CRYPTO_TYPE_SIGN & CRYPTO_TYPE_VERIFY) */
#define CRYPTO_AS_RSA 2 /* RSA */
#define CRYPTO_AS_DSA 3 /* DSA */
#define CRYPTO_AS_GOST 4 /* GOST */
/* Currently defined algorithm IDs (for types
CRYPTO_TYPE_COMPRESS & CRYPTO_TYPE_UNCOMPRESS) */
#define CRYPTO_AC_DUMMY 1 /* no compression */
#define CRYPTO_AC_DEFLATE 2 /* Deflate */
#define CRYPTO_AC_LZS 3 /* LZS */
/* Currently defined algorithm IDs (for type CRYPTO_TYPE_HASH) */
#define CRYPTO_AH_MD5 1 /* MD5 */
#define CRYPTO_AH_SHA 2 /* SHA-1 */
#define CRYPTO_AH_GOST 3 /* GOST */
/* Currently defined algorithm IDs (for type CRYPTO_TYPE_RANDOM) */
#define CRYPTO_AR_UNKNOWN 1
/* Currently defined plugin flags */
#define CRYPTO_PLUGIN_HARDWARE 1 /* plugin uses hdw */
/* TBD more */
/* Currently defined algorithm flags */
#define CRYPTO_ALG_HARDWARE 1 /* algorithm implemented
in hardware */
#define CRYPTO_ALG_MULTITHREADED 2 /* implementation allows
multithreading */
/* TBD more */
/* Currently defined parameters identifiers for CryptoControl */
#define CRYPTO_PARAM_KEY 1 /* Only for CRYPTO_GET -
get current key */
/* TBD more */
typedef struct tag_CryptoAlgInfo {
long status; /* Algorithm status */
long type; /* algorithm type (One of
CRYPTO_TYPE_XXX) */
long id; /* algorithm ID */
long group; /* algorithm group */
long version; /* algorithm version
(CRYPTO_VER) */
long flags; /* algorithm flags
(CRYPTO_ALG_XXX) */
long maxcontexts; /* max number of cipher states
supported (0 - any) */
char name[CRYPTO_ALG_NAME_LEN]; /* algorithm name */
/* CRYPT SIGN COMPRESS HASH RANDOM */
/* DECRYPT VERIFY */
long blocklen; /* blklen (blklen) inlen blklen - */
long keylen; /* keylen keylen - - seedlen */
long outlen; /* outlen (signlen) outlen hashlen randlen */
long milen; /* milen (param) - - - */
} CryptoAlgInfo;
typedef struct tag_CryptoPluginInfo {
long cpi_version; /* Crypto PI version (currently
CRYPTO_VER(1,0)) */
long status; /* Plugin status */
char name[CRYPTO_PLUGIN_NAME_LEN]; /* plugin text
description */
long version; /* plugin version
(CRYPTO_VER) */
long flags; /* plugin flags
(CRYPTO_PLUGIN_XXX) */
long number_of_algs; /* number of AlgInfo structures
followed (min 1) */
CryptoAlgInfo algs[1]; /* array of AlgInfo structures
(min 1) */
} CryptoPluginInfo;
#ifdef __cplusplus
extern "C" {
#endif
/* CryptoPlugin initialization. Returns pointer to CryptoPluginInfo
structure on success or NULL on fatal error. */
CryptoPluginInfo *CryptoPluginInit(
void *param);/* Ptr to OS parameters
(platform-specific) */
/* Plugin deinitialization */
CRYPTO_STATUS CryptoPluginFini(void);
/* Get new algorithm instance (cipher state) */
CRYPTO_STATUS CryptoOpen(
CRYPTO_HANDLE *state, /* Pointer to cipher state
handle (filled on exit) */
long algnum, /* Algorithm number in
CryptoPluginInfo structure */
const char *key); /* key (in plain) */
/* Reinitialize algorithm instance */
CRYPTO_STATUS CryptoReOpen(
CRYPTO_HANDLE state, /* current cipher state handle */
const char *key); /* key (in plain) */
/* Destroy algorithm instance */
CRYPTO_STATUS CryptoClose(
CRYPTO_HANDLE state); /* Handle of cipher state */
/* Check key for possible weakness */
CRYPTO_STATUS CryptoCheckForWeakKey(
long algnum, /* Algorithm number in
CryptoPluginInfo structure */
const char *key); /* Proposed key */
/* Perform CryptoTransform (depends on cipher state type) */
CRYPTO_STATUS CryptoTransform(
CRYPTO_HANDLE state, /* Cipher state handle */
const char *inbuff,/* input data */
long inlen, /* input data length */
char *outbuff,/* output buffer */
long *outlen,/* On entry - output buffer
length, on exit - number of
bytes written to outbuff */
char *mi); /* Message indicator */
/* Algorithm control */
CRYPTO_STATUS CryptoControl(
CRYPTO_HANDLE state, /* Cipher state handle */
long cmd, /* Control command */
long param, /* Parameter id */
char val, /* Parameter value */
long *len); /* For CRYPTO_GET: on entry -
val buffer length, on exit -
number of bytes written to
val; for CRYPTO_SET: length
of value to set */
#ifdef __cplusplus
}
#endif
#endif /* __CRYPTPI_H */
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