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.\" ========================================================================
.\"
.IX Title "EVP_MAC-KMAC 7SSL"
.TH EVP_MAC-KMAC 7SSL "2024-10-27" "3.0.15" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH "NAME"
EVP_MAC\-KMAC, EVP_MAC\-KMAC128, EVP_MAC\-KMAC256
\&\- The KMAC EVP_MAC implementations
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Support for computing \s-1KMAC\s0 MACs through the \fB\s-1EVP_MAC\s0\fR \s-1API.\s0
.SS "Identity"
.IX Subsection "Identity"
These implementations are identified with one of these names and
properties, to be used with \fBEVP_MAC_fetch()\fR:
.ie n .IP """\s-1KMAC\-128"",\s0 ""provider=default"" or ""provider=fips""" 4
.el .IP "``\s-1KMAC\-128'',\s0 ``provider=default'' or ``provider=fips''" 4
.IX Item "KMAC-128, provider=default or provider=fips"
.PD 0
.ie n .IP """\s-1KMAC\-256"",\s0 ""provider=default"" or ""provider=fips""" 4
.el .IP "``\s-1KMAC\-256'',\s0 ``provider=default'' or ``provider=fips''" 4
.IX Item "KMAC-256, provider=default or provider=fips"
.PD
.SS "Supported parameters"
.IX Subsection "Supported parameters"
The general description of these parameters can be found in
\&\*(L"\s-1PARAMETERS\*(R"\s0 in \s-1\fBEVP_MAC\s0\fR\|(3).
.PP
All these parameters (except for \*(L"block-size\*(R") can be set with
\&\fBEVP_MAC_CTX_set_params()\fR.
Furthermore, the \*(L"size\*(R" parameter can be retrieved with
\&\fBEVP_MAC_CTX_get_params()\fR, or with \fBEVP_MAC_CTX_get_mac_size()\fR.
The length of the \*(L"size\*(R" parameter should not exceed that of a \fBsize_t\fR.
Likewise, the \*(L"block-size\*(R" parameter can be retrieved with
\&\fBEVP_MAC_CTX_get_params()\fR, or with \fBEVP_MAC_CTX_get_block_size()\fR.
.ie n .IP """key"" (\fB\s-1OSSL_MAC_PARAM_KEY\s0\fR) <octet string>" 4
.el .IP "``key'' (\fB\s-1OSSL_MAC_PARAM_KEY\s0\fR) <octet string>" 4
.IX Item "key (OSSL_MAC_PARAM_KEY) <octet string>"
Sets the \s-1MAC\s0 key.
Setting this parameter is identical to passing a \fIkey\fR to \fBEVP_MAC_init\fR\|(3).
The length of the key (in bytes) must be in the range 4...512.
.ie n .IP """custom"" (\fB\s-1OSSL_MAC_PARAM_CUSTOM\s0\fR) <octet string>" 4
.el .IP "``custom'' (\fB\s-1OSSL_MAC_PARAM_CUSTOM\s0\fR) <octet string>" 4
.IX Item "custom (OSSL_MAC_PARAM_CUSTOM) <octet string>"
Sets the customization string.
It is an optional value with a length of at most 512 bytes, and is
empty by default.
.ie n .IP """size"" (\fB\s-1OSSL_MAC_PARAM_SIZE\s0\fR) <unsigned integer>" 4
.el .IP "``size'' (\fB\s-1OSSL_MAC_PARAM_SIZE\s0\fR) <unsigned integer>" 4
.IX Item "size (OSSL_MAC_PARAM_SIZE) <unsigned integer>"
Sets the \s-1MAC\s0 size.
By default, it is 32 for \f(CW\*(C`KMAC\-128\*(C'\fR and 64 for \f(CW\*(C`KMAC\-256\*(C'\fR.
.ie n .IP """block-size"" (\fB\s-1OSSL_MAC_PARAM_BLOCK_SIZE\s0\fR) <unsigned integer>" 4
.el .IP "``block-size'' (\fB\s-1OSSL_MAC_PARAM_BLOCK_SIZE\s0\fR) <unsigned integer>" 4
.IX Item "block-size (OSSL_MAC_PARAM_BLOCK_SIZE) <unsigned integer>"
Gets the \s-1MAC\s0 block size.
It is 168 for \f(CW\*(C`KMAC\-128\*(C'\fR and 136 for \f(CW\*(C`KMAC\-256\*(C'\fR.
.ie n .IP """xof"" (\fB\s-1OSSL_MAC_PARAM_XOF\s0\fR) <integer>" 4
.el .IP "``xof'' (\fB\s-1OSSL_MAC_PARAM_XOF\s0\fR) <integer>" 4
.IX Item "xof (OSSL_MAC_PARAM_XOF) <integer>"
The \*(L"xof\*(R" parameter value is expected to be 1 or 0. Use 1 to enable \s-1XOF\s0 mode.
The default value is 0.
.PP
The \*(L"custom\*(R" parameter must be set as part of or before the \fBEVP_MAC_init()\fR call.
The \*(L"xof\*(R" and \*(L"size\*(R" parameters can be set at any time before \fBEVP_MAC_final()\fR.
The \*(L"key\*(R" parameter is set as part of the \fBEVP_MAC_init()\fR call, but can be
set before it instead.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
.Vb 2
\&  #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;
\&  }
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBEVP_MAC_CTX_get_params\fR\|(3), \fBEVP_MAC_CTX_set_params\fR\|(3),
\&\*(L"\s-1PARAMETERS\*(R"\s0 in \s-1\fBEVP_MAC\s0\fR\|(3), \s-1\fBOSSL_PARAM\s0\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2018\-2021 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the Apache License 2.0 (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.
