1=pod
2
3=head1 NAME
4
5EVP_MAC-KMAC, EVP_MAC-KMAC128, EVP_MAC-KMAC256
6- The KMAC EVP_MAC implementations
7
8=head1 DESCRIPTION
9
10Support for computing KMAC MACs through the B<EVP_MAC> API.
11
12=head2 Identity
13
14These implementations are identified with one of these names and
15properties, to be used with EVP_MAC_fetch():
16
17=over 4
18
19=item "KMAC-128", "provider=default" or "provider=fips"
20
21=item "KMAC-256", "provider=default" or "provider=fips"
22
23=back
24
25=head2 Supported parameters
26
27The general description of these parameters can be found in
28L<EVP_MAC(3)/PARAMETERS>.
29
30All these parameters (except for "block-size") can be set with
31EVP_MAC_CTX_set_params().
32Furthermore, the "size" parameter can be retrieved with
33EVP_MAC_CTX_get_params(), or with EVP_MAC_CTX_get_mac_size().
34The length of the "size" parameter should not exceed that of a B<size_t>.
35Likewise, the "block-size" parameter can be retrieved with
36EVP_MAC_CTX_get_params(), or with EVP_MAC_CTX_get_block_size().
37
38
39=over 4
40
41=item "key" (B<OSSL_MAC_PARAM_KEY>) <octet string>
42
43Sets the MAC key.
44Setting this parameter is identical to passing a I<key> to L<EVP_MAC_init(3)>.
45The length of the key (in bytes) must be in the range 4...512.
46
47=item "custom" (B<OSSL_MAC_PARAM_CUSTOM>) <octet string>
48
49Sets the customization string.
50It is an optional value with a length of at most 512 bytes, and is
51empty by default.
52
53=item "size" (B<OSSL_MAC_PARAM_SIZE>) <unsigned integer>
54
55Sets the MAC size.
56By default, it is 32 for C<KMAC-128> and 64 for C<KMAC-256>.
57
58=item "block-size" (B<OSSL_MAC_PARAM_BLOCK_SIZE>) <unsigned integer>
59
60Gets the MAC block size.
61It is 168 for C<KMAC-128> and 136 for C<KMAC-256>.
62
63=item "xof" (B<OSSL_MAC_PARAM_XOF>) <integer>
64
65The "xof" parameter value is expected to be 1 or 0. Use 1 to enable XOF mode.
66The default value is 0.
67
68=back
69
70The "custom" parameter must be set as part of or before the EVP_MAC_init() call.
71The "xof" and "size" parameters can be set at any time before EVP_MAC_final().
72The "key" parameter is set as part of the EVP_MAC_init() call, but can be
73set before it instead.
74
75=head1 EXAMPLES
76
77  #include <openssl/evp.h>
78  #include <openssl/params.h>
79
80  static int do_kmac(const unsigned char *in, size_t in_len,
81                     const unsigned char *key, size_t key_len,
82                     const unsigned char *custom, size_t custom_len,
83                     int xof_enabled, unsigned char *out, int out_len)
84  {
85      EVP_MAC_CTX *ctx = NULL;
86      EVP_MAC *mac = NULL;
87      OSSL_PARAM params[4], *p;
88      int ret = 0;
89      size_t l = 0;
90
91      mac = EVP_MAC_fetch(NULL, "KMAC-128", NULL);
92      if (mac == NULL)
93          goto err;
94      ctx = EVP_MAC_CTX_new(mac);
95      /* The mac can be freed after it is used by EVP_MAC_CTX_new */
96      EVP_MAC_free(mac);
97      if (ctx == NULL)
98          goto err;
99
100      /*
101       * Setup parameters required before calling EVP_MAC_init()
102       * The parameters OSSL_MAC_PARAM_XOF and OSSL_MAC_PARAM_SIZE may also be
103       * used at this point.
104       */
105      p = params;
106      *p++ = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_KEY,
107                                               (void *)key, key_len);
108      if (custom != NULL && custom_len != 0)
109        *p++ = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_CUSTOM,
110                                                 (void *)custom, custom_len);
111      *p = OSSL_PARAM_construct_end();
112      if (!EVP_MAC_CTX_set_params(ctx, params))
113          goto err;
114
115      if (!EVP_MAC_init(ctx))
116          goto err;
117
118      /*
119       * Note: the following optional parameters can be set any time
120       * before EVP_MAC_final().
121       */
122      p = params;
123      *p++ = OSSL_PARAM_construct_int(OSSL_MAC_PARAM_XOF, &xof_enabled);
124      *p++ = OSSL_PARAM_construct_int(OSSL_MAC_PARAM_SIZE, &out_len);
125      *p = OSSL_PARAM_construct_end();
126      if (!EVP_MAC_CTX_set_params(ctx, params))
127          goto err;
128
129      /* The update may be called multiple times here for streamed input */
130      if (!EVP_MAC_update(ctx, in, in_len))
131          goto err;
132      if (!EVP_MAC_final(ctx, out, &l, out_len))
133          goto err;
134      ret = 1;
135  err:
136      EVP_MAC_CTX_free(ctx);
137      return ret;
138  }
139
140=head1 SEE ALSO
141
142L<EVP_MAC_CTX_get_params(3)>, L<EVP_MAC_CTX_set_params(3)>,
143L<EVP_MAC(3)/PARAMETERS>, L<OSSL_PARAM(3)>
144
145=head1 COPYRIGHT
146
147Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved.
148
149Licensed under the Apache License 2.0 (the "License").  You may not use
150this file except in compliance with the License.  You can obtain a copy
151in the file LICENSE in the source distribution or at
152L<https://www.openssl.org/source/license.html>.
153
154=cut
155