5 HMAC, HMAC_Init, HMAC_Update, HMAC_Final, HMAC_cleanup - HMAC message
10 #include <openssl/hmac.h>
12 unsigned char *HMAC(const EVP_MD *evp_md, const void *key,
13 int key_len, const unsigned char *d, int n,
14 unsigned char *md, unsigned int *md_len);
16 void HMAC_Init(HMAC_CTX *ctx, const void *key, int key_len,
18 void HMAC_Update(HMAC_CTX *ctx, const unsigned char *data, int len);
19 void HMAC_Final(HMAC_CTX *ctx, unsigned char *md, unsigned int *len);
21 void HMAC_cleanup(HMAC_CTX *ctx);
25 HMAC is a MAC (message authentication code), i.e. a keyed hash
26 function used for message authentication, which is based on a hash
29 HMAC() computes the message authentication code of the B<n> bytes at
30 B<d> using the hash function B<evp_md> and the key B<key> which is
31 B<key_len> bytes long.
33 It places the result in B<md> (which must have space for the output of
34 the hash function, which is no more than B<EVP_MAX_MD_SIZE> bytes).
35 If B<md> is NULL, the digest is placed in a static array. The size of
36 the output is placed in B<md_len>, unless it is B<NULL>.
38 B<evp_md> can be EVP_sha1(), EVP_ripemd160() etc.
39 B<key> and B<evp_md> may be B<NULL> if a key and hash function have
40 been set in a previous call to HMAC_Init() for that B<HMAC_CTX>.
42 HMAC_cleanup() erases the key and other data from the B<HMAC_CTX>.
44 The following functions may be used if the message is not completely
47 HMAC_Init() initializes a B<HMAC_CTX> structure to use the hash
48 function B<evp_md> and the key B<key> which is B<key_len> bytes long.
50 HMAC_Update() can be called repeatedly with chunks of the message to
51 be authenticated (B<len> bytes at B<data>).
53 HMAC_Final() places the message authentication code in B<md>, which
54 must have space for the hash function output.
58 HMAC() returns a pointer to the message authentication code.
60 HMAC_Init(), HMAC_Update(), HMAC_Final() and HMAC_cleanup() do not
69 L<sha(3)|sha(3)>, L<evp(3)|evp(3)>
73 HMAC(), HMAC_Init(), HMAC_Update(), HMAC_Final() and HMAC_cleanup()
74 are available since SSLeay 0.9.0.