Cryptography and SSL/TLS Toolkit



EVP_MAC-HMAC - The HMAC EVP_MAC implementation


Support for computing HMAC MACs through the EVP_MAC API.


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).

The following parameter can be set with EVP_MAC_CTX_set_params():

"key" (OSSL_MAC_PARAM_KEY) <octet string>
"flags" (OSSL_MAC_PARAM_FLAGS) <octet string>
"digest" (OSSL_MAC_PARAM_DIGEST) <UTF8 string>
"properties" (OSSL_MAC_PARAM_PROPERTIES) <UTF8 string>

The "flags" parameter is passed directly to HMAC_CTX_set_flags().

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_size(). The length of the "size" parameter is equal to that of an unsigned int.


EVP_MAC_CTX_get_params(3), EVP_MAC_CTX_set_params(3), "PARAMETERS" in EVP_MAC(3), OSSL_PARAM(3), HMAC(3)

Copyright 2018-2020 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