5 HMAC, HMAC_CTX_new, HMAC_CTX_reset, HMAC_CTX_free, HMAC_Init, HMAC_Init_ex, 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 HMAC_CTX *HMAC_CTX_new(void);
16 int HMAC_CTX_reset(HMAC_CTX *ctx);
18 int HMAC_Init_ex(HMAC_CTX *ctx, const void *key, int key_len,
19 const EVP_MD *md, ENGINE *impl);
20 int HMAC_Update(HMAC_CTX *ctx, const unsigned char *data, int len);
21 int HMAC_Final(HMAC_CTX *ctx, unsigned char *md, unsigned int *len);
23 void HMAC_CTX_free(HMAC_CTX *ctx);
27 #if OPENSSL_API_COMPAT < 0x10100000L
28 int HMAC_Init(HMAC_CTX *ctx, const void *key, int key_len,
34 HMAC is a MAC (message authentication code), i.e. a keyed hash
35 function used for message authentication, which is based on a hash
38 HMAC() computes the message authentication code of the B<n> bytes at
39 B<d> using the hash function B<evp_md> and the key B<key> which is
40 B<key_len> bytes long.
42 It places the result in B<md> (which must have space for the output of
43 the hash function, which is no more than B<EVP_MAX_MD_SIZE> bytes).
44 If B<md> is NULL, the digest is placed in a static array. The size of
45 the output is placed in B<md_len>, unless it is B<NULL>.
47 B<evp_md> can be EVP_sha1(), EVP_ripemd160() etc.
49 HMAC_CTX_new() creates a new HMAC_CTX in heap memory.
51 HMAC_CTX_reset() zeroes an existing B<HMAC_CTX> and associated
52 resources, making it suitable for new computations as if it was newly
53 created with HMAC_CTX_new().
55 HMAC_CTX_free() erases the key and other data from the B<HMAC_CTX>,
56 releases any associated resources and finally frees the B<HMAC_CTX>
59 The following functions may be used if the message is not completely
62 HMAC_Init() initializes a B<HMAC_CTX> structure to use the hash
63 function B<evp_md> and the key B<key> which is B<key_len> bytes
64 long. It is deprecated and only included for backward compatibility
67 HMAC_Init_ex() initializes or reuses a B<HMAC_CTX> structure to use
68 the function B<evp_md> and key B<key>. Either can be NULL, in which
69 case the existing one will be reused. B<ctx> must have been created
70 with HMAC_CTX_new() before the first use of an B<HMAC_CTX> in this
71 function. B<N.B. HMAC_Init() had this undocumented behaviour in
72 previous versions of OpenSSL - failure to switch to HMAC_Init_ex() in
73 programs that expect it will cause them to stop working>.
75 HMAC_Update() can be called repeatedly with chunks of the message to
76 be authenticated (B<len> bytes at B<data>).
78 HMAC_Final() places the message authentication code in B<md>, which
79 must have space for the hash function output.
83 HMAC() returns a pointer to the message authentication code or NULL if
86 HMAC_CTX_new() returns a pointer to a new B<HMAC_CTX> on success or
87 B<NULL> if an error occurred.
89 HMAC_CTX_reset(), HMAC_Init_ex(), HMAC_Update() and HMAC_Final() return 1
90 for success or 0 if an error occurred.
92 HMAC_CTX_free() do not return values.
104 HMAC_CTX_init() was replaced with HMAC_CTX_reset() in OpenSSL versions 1.1.
106 HMAC_CTX_cleanup() existed in OpenSSL versions before 1.1.
108 HMAC_CTX_new() and HMAC_CTX_free() are new in OpenSSL version 1.1.
110 HMAC_Init_ex(), HMAC_Update() and HMAC_Final() did not return values in
111 versions of OpenSSL before 1.0.0.
115 Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
117 Licensed under the OpenSSL license (the "License"). You may not use
118 this file except in compliance with the License. You can obtain a copy
119 in the file LICENSE in the source distribution or at
120 L<https://www.openssl.org/source/license.html>.