5 HMAC, HMAC_Init, HMAC_Update, HMAC_Final - HMAC message authentication code
9 #include <openssl/hmac.h>
11 unsigned char *HMAC(const EVP_MD *evp_md, const void *key,
12 int key_len, const unsigned char *d, int n,
13 unsigned char *md, unsigned int *md_len);
15 void HMAC_Init(HMAC_CTX *ctx, const void *key, int key_len,
17 void HMAC_Update(HMAC_CTX *ctx, const unsigned char *data, int len);
18 void HMAC_Final(HMAC_CTX *ctx, unsigned char *md, unsigned int *len);
20 void HMAC_cleanup(HMAC_CTX *ctx);
24 HMAC is a MAC (message authentication code), i.e. a keyed hash
25 function used for message authentication, which is based on a hash
28 HMAC() computes the message authentication code of the B<n> bytes at
29 B<d> using the hash function B<evp_md> and the key B<key> which is
30 B<key_len> bytes long.
32 It places the result in B<md> (which must have space for the output of
33 the hash function, which is no more than B<EVP_MAX_MD_SIZE> bytes).
34 If B<md> is NULL, the digest is placed in a static array. The size of
35 the output is placed in B<md_len>, unless it is B<NULL>.
37 B<evp_md> can be EVP_sha1(), EVP_ripemd160() etc.
38 B<key> and B<evp_md> may be B<NULL> if a key and hash function have
39 been set in a previous call to HMAC_Init() for that B<HMAC_CTX>.
41 HMAC_cleanup() erases the key and other data from the B<HMAC_CTX>.
43 The following functions may be used if the message is not completely
46 HMAC_Init() initializes a B<HMAC_CTX> structure to use the hash
47 function B<evp_md> and the key B<key> which is B<key_len> bytes long.
49 HMAC_Update() can be called repeatedly with chunks of the message to
50 be authenticated (B<len> bytes at B<data>).
52 HMAC_Final() places the message authentication code in B<md>, which
53 must have space for the hash function output.
57 HMAC() returns a pointer to the message authentication code.
59 HMAC_Init(), HMAC_Update(), HMAC_Final() and HMAC_cleanup() do not
68 L<sha(3)|sha(3)>, L<evp(3)|evp(3)>
72 HMAC(), HMAC_Init(), HMAC_Update(), HMAC_Final() and HMAC_cleanup()
73 are available since SSLeay 0.9.0.