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author | Ulf Möller <ulf@openssl.org> | 2000-02-03 18:22:01 +0000 |
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committer | Ulf Möller <ulf@openssl.org> | 2000-02-03 18:22:01 +0000 |
commit | 9dbc41d7eed7d69da54dc81082794845c50ad482 (patch) | |
tree | 3c59e6df13deb5eed99501dc7fffac681fb7e1eb /doc/crypto/hmac.pod | |
parent | 82fc1d9c28e834549f61e4c91b3f6bbdf4c48153 (diff) |
Document hash functions.
Diffstat (limited to 'doc/crypto/hmac.pod')
-rw-r--r-- | doc/crypto/hmac.pod | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/doc/crypto/hmac.pod b/doc/crypto/hmac.pod new file mode 100644 index 0000000000..45b6108c39 --- /dev/null +++ b/doc/crypto/hmac.pod @@ -0,0 +1,75 @@ +=pod + +=head1 NAME + +HMAC, HMAC_Init, HMAC_Update, HMAC_Final - HMAC message authentication code + +=head1 SYNOPSIS + + #include <openssl/hmac.h> + + unsigned char *HMAC(const EVP_MD *evp_md, const void *key, + int key_len, const unsigned char *d, int n, + unsigned char *md, unsigned int *md_len); + + void HMAC_Init(HMAC_CTX *ctx, const void *key, int key_len, + const EVP_MD *md); + void HMAC_Update(HMAC_CTX *ctx, const unsigned char *data, int len); + void HMAC_Final(HMAC_CTX *ctx, unsigned char *md, unsigned int *len); + + void HMAC_cleanup(HMAC_CTX *ctx); + +=head1 DESCRIPTION + +HMAC is a MAC (message authentication code), i.e. a keyed hash +function used for message authentication, which is based on a hash +function. + +HMAC() computes the message authentication code of the B<n> bytes at +B<d> using the hash function B<evp_md> and the key B<key> which is +B<key_len> bytes long. + +It places the result in B<md> (which must have space for the output of +the hash function, which is no more than B<EVP_MAX_MD_SIZE> bytes). +If B<md> is NULL, the digest is placed in a static array. The size of +the output is placed in B<md_len>, unless it is B<NULL>. + +B<evp_md> can be EVP_sha1(), EVP_ripemd160() etc. +B<key> and B<evp_md> may be B<NULL> if a key and hash function have +been set in a previous call to HMAC_Init() for that B<HMAC_CTX>. + +HMAC_cleanup() erases the key and other data from the B<HMAC_CTX>. + +The following functions may be used if the message is not completely +stored in memory: + +HMAC_Init() initializes a B<HMAC_CTX> structure to use the hash +function B<evp_md> and the key B<key> which is B<key_len> bytes long. + +HMAC_Update() can be called repeatedly with chunks of the message to +be authenticated (B<len> bytes at B<data>). + +HMAC_Final() places the message authentication code in B<md>, which +must have space for the hash function output. + +=head1 RETURN VALUES + +HMAC() returns a pointer to the message authentication code. + +HMAC_Init(), HMAC_Update(), HMAC_Final() and HMAC_cleanup() do not +return values. + +=head1 CONFORMING TO + +RFC 2104 + +=head1 SEE ALSO + +L<sha(3)|sha(3)>, L<evp(3)|evp(3)> + +=head1 HISTORY + +HMAC(), HMAC_Init(), HMAC_Update(), HMAC_Final() and HMAC_cleanup() +are available since SSLeay 0.9.0. + +=cut |