# phpman > man > EVP_MAC-KMAC(7)

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



## NAME
       EVP_MAC-KMAC, EVP_MAC-KMAC128, EVP_MAC-KMAC256 - The KMAC EVP_MAC implementations

## DESCRIPTION
       Support for computing KMAC MACs through the **EVP**___**MAC** API.

### Identity
       These implementations are identified with one of these names and properties, to be used with
       **EVP**___**MAC**___**fetch()**:

       "KMAC-128", "provider=default" or "provider=fips"
       "KMAC-256", "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/MAC/3/markdown).

       All these parameters can be set with **EVP**___**MAC**___**CTX**___**set**___**params()**.  Furthermore, the "size"
       parameter can be retrieved with **EVP**___**MAC**___**CTX**___**get**___**params()**, or with **EVP**___**MAC**___**CTX**___**get**___**mac**___**size()**.
       The length of the "size" parameter should not exceed that of a **size**___**t**.  Likewise, the "block-
       size" parameter can be retrieved with **EVP**___**MAC**___**CTX**___**get**___**params()**, or with
       **EVP**___**MAC**___**CTX**___**get**___**block**___**size()**.

       "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/init/3/markdown).

       "custom" (**OSSL**___**MAC**___**PARAM**___**CUSTOM**) <octet string>
           Sets the custom value.  It is an optional value of at most 256 bytes, and is empty by
           default.

       "size" (**OSSL**___**MAC**___**PARAM**___**SIZE**) <unsigned integer>
           Sets the MAC size.  By default, it is 16 for "KMAC-128" and 32 for "KMAC-256".

       "block-size" (**OSSL**___**MAC**___**PARAM**___**SIZE**) <unsigned integer>
           Gets the MAC block size.  By default, it is 168 for "KMAC-128" and 136 for "KMAC-256".

       "xof" (**OSSL**___**MAC**___**PARAM**___**XOF**) <integer>
           The "xof" parameter value is expected to be 1 or 0. Use 1 to enable XOF mode.  The
           default value is 0.

       The "custom" parameter must be set as part of or before the **EVP**___**MAC**___**init()** call.  The "xof"
       and "size" parameters can be set at any time before **EVP**___**MAC**___**final()**.  The "key" parameter is
       set as part of the **EVP**___**MAC**___**init()** call, but can be set before it instead.

## EXAMPLES
         #include <openssl/evp.h>
         #include <openssl/params.h>

         static int do_kmac(const unsigned char *in, size_t in_len,
                            const unsigned char *key, size_t key_len,
                            const unsigned char *custom, size_t custom_len,
                            int xof_enabled, unsigned char *out, int out_len)
         {
             EVP_MAC_CTX *ctx = NULL;
             EVP_MAC *mac = NULL;
             OSSL_PARAM params[4], *p;
             int ret = 0;
             size_t l = 0;

             mac = EVP_MAC_fetch(NULL, "KMAC-128", NULL);
             if (mac == NULL)
                 goto err;
             ctx = EVP_MAC_CTX_new(mac);
             /* The mac can be freed after it is used by EVP_MAC_CTX_new */
             EVP_MAC_free(mac);
             if (ctx == NULL)
                 goto err;

             /*
              * Setup parameters required before calling EVP_MAC_init()
              * The parameters OSSL_MAC_PARAM_XOF and OSSL_MAC_PARAM_SIZE may also be
              * used at this point.
              */
             p = params;
             *p++ = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_KEY,
                                                      (void *)key, key_len);
             if (custom != NULL && custom_len != 0)
               *p++ = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_CUSTOM,
                                                        (void *)custom, custom_len);
             *p = OSSL_PARAM_construct_end();
             if (!EVP_MAC_CTX_set_params(ctx, params))
                 goto err;

             if (!EVP_MAC_init(ctx))
                 goto err;

             /*
              * Note: the following optional parameters can be set any time
              * before EVP_MAC_final().
              */
             p = params;
             *p++ = OSSL_PARAM_construct_int(OSSL_MAC_PARAM_XOF, &xof_enabled);
             *p++ = OSSL_PARAM_construct_int(OSSL_MAC_PARAM_SIZE, &out_len);
             *p = OSSL_PARAM_construct_end();
             if (!EVP_MAC_CTX_set_params(ctx, params))
                 goto err;

             /* The update may be called multiple times here for streamed input */
             if (!EVP_MAC_update(ctx, in, in_len))
                 goto err;
             if (!EVP_MAC_final(ctx, out, &l, out_len))
                 goto err;
             ret = 1;
         err:
             EVP_MAC_CTX_free(ctx);
             return ret;
         }

## SEE ALSO
       **EVP**___**MAC**___**CTX**___**get**___**[params**(3)](https://www.chedong.com/phpMan.php/man/params/3/markdown), **EVP**___**MAC**___**CTX**___**set**___**[params**(3)](https://www.chedong.com/phpMan.php/man/params/3/markdown), "PARAMETERS" in **EVP**___**[MAC**(3)](https://www.chedong.com/phpMan.php/man/MAC/3/markdown),
       **OSSL**___**[PARAM**(3)](https://www.chedong.com/phpMan.php/man/PARAM/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>>.



3.0.2                                        2026-04-07                           [EVP_MAC-KMAC(7SSL)](https://www.chedong.com/phpMan.php/man/EVPMAC-KMAC/7SSL/markdown)