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EVP_MAC-GMAC(7SSL)                  OpenSSL                  EVP_MAC-GMAC(7SSL)

NAME
       EVP_MAC-GMAC - The GMAC EVP_MAC implementation

DESCRIPTION
       Support for computing GMAC MACs through the EVP_MAC API.

       This implementation uses EVP_CIPHER functions to get access to the
       underlying cipher.

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

       "GMAC", "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>
           Sets  the MAC key.  Setting this parameter is identical to passing a
           key to EVP_MAC_init(3).

       "iv" (OSSL_MAC_PARAM_IV) <octet string>
           Sets the IV of the underlying cipher, when applicable.

       "cipher" (OSSL_MAC_PARAM_CIPHER) <UTF8 string>
           Sets the name of the underlying cipher to be used.

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

       The following parameters can be retrieved with EVP_MAC_CTX_get_params():

       "size" (OSSL_MAC_PARAM_SIZE) <unsigned integer>
           Gets the MAC size.

       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.

SEE ALSO
       EVP_MAC_CTX_get_params(3),  EVP_MAC_CTX_set_params(3),  "PARAMETERS"  in
       EVP_MAC(3), OSSL_PARAM(3)

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>.

3.5.4                              2025-09-30                EVP_MAC-GMAC(7SSL)

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