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Chapter 2 Algorithm Info Types 91
AI_HMAC
AI_HMAC
Purpose:
This AI allows you to create a message authentication code using a keyed hashing
algorithm called Hash-Based Message Authentication Code (HMAC).
Type of information this allows you to use:
the specified digest algorithm for performing HMAC as defined in the SET draft
standard, a subset of the Draft-IETF-IPSEC-AH-HMAC-SHA-04.
Format of info supplied to B_SetAlgorithmInfo:
pointer to a B_DIGEST_SPECIFIER structure:
Crypto-C 4.3 supports
AI_SHA1 and AI_MD5 as a
digestInfoType
, with NULL_PTR as the
digestInfoParams
.
Format of info returned by B_GetAlgorithmInfo:
pointer to a B_DIGEST_SPECIFIER structure.
Crypto-C procedures to use with algorithm object:
B_DigestInit, B_DigestUpdate, and B_DigestFinal. You must pass a key object
compatible with
KI_Item with at least one byte of keying material as the
keyObject
argument in
B_DigestInit. It is recommended that minimally 20 bytes of key be used
when SHA1 is the hash function. More bytes are recommended if the key bytes are
weakly random (low entropy keys).
Algorithm methods to include in application’s algorithm chooser:
The appropriate AM for the digest specified; for instance, AM_SHA when the
digestInfoType
is AI_SHA1, and AM_MD5 for AI_MD5.
typedef struct {
B_INFO_TYPE digestInfoType;
POINTER digestInfoParams;
} B_DIGEST_SPECIFIER;