openssl/doc/crypto/hmac.pod
Richard Levitte e1b78bc64d In the name section, all the functions described shoud be enumerated.
This will also make it much simpler to generate softlinks name like
each function to man-pages containing the info.
2000-09-14 21:23:28 +00:00

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=pod
=head1 NAME
HMAC, HMAC_Init, HMAC_Update, HMAC_Final, HMAC_cleanup - 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