# man > EVP_MAC-HMAC(7SSL)

[_EVP_MAC-HMAC_(7SSL)](https://www.chedong.com/phpMan.php/man/EVPMAC-HMAC/7SSL/markdown)                             OpenSSL                            [_EVP_MAC-HMAC_(7SSL)](https://www.chedong.com/phpMan.php/man/EVPMAC-HMAC/7SSL/markdown)

## NAME
       EVP_MAC-HMAC - The HMAC EVP_MAC implementation

## DESCRIPTION
       Support for computing HMAC MACs through the **EVP_MAC **API.

       This implementation uses EVP_MD functions to get access to the underlying digest.

### Identity
       This implementation is identified with this name and properties, to be used with
       **EVP_MAC_fetch()**:

       "HMAC", "provider=default" or "provider=fips"

### Supported parameters
       The general description of these parameters can be found in "PARAMETERS" in [**EVP_MAC**(3)](https://www.chedong.com/phpMan.php/man/EVPMAC/3/markdown).

       The following parameter can be set with **EVP_MAC_CTX_set_params()**:

       "key" (**OSSL_MAC_PARAM_KEY**) <octet string>
           Sets   the   MAC  key.   Setting  this  parameter  is  identical  to  passing  a  _key_  to
           [**EVP_MAC_init**(3)](https://www.chedong.com/phpMan.php/man/EVPMACinit/3/markdown).

       "digest" (**OSSL_MAC_PARAM_DIGEST**) <UTF8 string>
           Sets the name of the underlying digest to be used.

       "properties" (**OSSL_MAC_PARAM_PROPERTIES**) <UTF8 string>
           Sets the properties to be queried when trying to fetch the underlying digest.  This  must
           be  given  together with the digest naming parameter ("digest", or **OSSL_MAC_PARAM_DIGEST**)
           to be considered valid.

       "digest-noinit" (**OSSL_MAC_PARAM_DIGEST_NOINIT**) <integer>
           A flag to set the MAC digest to not initialise the  implementation  specific  data.   The
           value 0 or 1 is expected.

       "digest-oneshot" (**OSSL_MAC_PARAM_DIGEST_ONESHOT**) <integer>
           A flag to set the MAC digest to be a one-shot operation.  The value 0 or 1 is expected.

       "tls-data-size" (**OSSL_MAC_PARAM_TLS_DATA_SIZE**) <unsigned integer>

       The following parameter can be retrieved with **EVP_MAC_CTX_get_params()**:

       "size" (**OSSL_MAC_PARAM_SIZE**) <unsigned integer>
           The  "size"  parameter can also be retrieved with **EVP_MAC_CTX_get_mac_size()**.  The length
           of the "size" parameter is equal to that of an **unsigned int**.

       "block-size" (**OSSL_MAC_PARAM_BLOCK_SIZE**) <unsigned integer>
           Gets the MAC  block  size.   The  "block-size"  parameter  can  also  be  retrieved  with
           **EVP_MAC_CTX_get_block_size()**.

## SEE ALSO
       [**EVP_MAC_CTX_get_params**(3)](https://www.chedong.com/phpMan.php/man/EVPMACCTXgetparams/3/markdown),    [**EVP_MAC_CTX_set_params**(3)](https://www.chedong.com/phpMan.php/man/EVPMACCTXsetparams/3/markdown),    "PARAMETERS"    in    [**EVP_MAC**(3)](https://www.chedong.com/phpMan.php/man/EVPMAC/3/markdown),
       [**OSSL_PARAM**(3)](https://www.chedong.com/phpMan.php/man/OSSLPARAM/3/markdown), [**HMAC**(3)](https://www.chedong.com/phpMan.php/man/HMAC/3/markdown)

## COPYRIGHT
       Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use this file  except  in
       compliance  with  the  License.   You  can  obtain  a  copy in the file LICENSE in the source
       distribution or at <<https://www.openssl.org/source/license.html>>.

3.0.13                                       2026-07-29                           [_EVP_MAC-HMAC_(7SSL)](https://www.chedong.com/phpMan.php/man/EVPMAC-HMAC/7SSL/markdown)