Keyed-hash message authentication code
A
keyed-hash message authentication code, or
HMAC, is a type of
message authentication code (MAC) calculated using a cryptographic
hash function in combination with a secret
key. As with any MAC, it may be used to simultaneously verify both the
data integrity and the
authenticity of a
message. Any iterative cryptographic hash function, e.g.,
SHA-1,
RIPEMD-160, may be used in the calculation of an HMAC; the cryptographic strength of the HMAC depends upon the cryptographic strength of the underlying hash function and on the size and quality of the key.
The construction and analysis of HMACs was first published in 1996 by Mihir Bellare, Ran Canetti, and Hugo Krawczyk, who also authored RFC 2104. FIPS PUB 198 generalizes and standardizes the use of HMACs.
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