Availability::- use_module(library(sha)).(can be autoloaded)
hmac_sha(+Key,
+Data, -HMAC, +Options)Quoting Wikipedia:
``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,
such as MD5 or SHA-1, may be used in the calculation of an HMAC; the
resulting MAC algorithm is termed HMAC-MD5 or HMAC-SHA-1 accordingly.
The cryptographic strength of the HMAC depends upon the cryptographic
strength of the underlying hash function, on the size and quality of the
key and the size of the hash output length in bits.''
Key and Data are either an atom, packed string
or list of character codes. HMAC is unified with a list of
integers representing the authentication code. Options is the
same as for
sha_hash/3,
but currently only sha1 and sha256 are
supported.