| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | EVP_KDF-KB - The Key-Based EVP_KDF implementation
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| 6 |
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| 7 | =head1 DESCRIPTION
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| 8 |
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| 9 | The EVP_KDF-KB algorithm implements the Key-Based key derivation function
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| 10 | (KBKDF). KBKDF derives a key from repeated application of a keyed MAC to an
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| 11 | input secret (and other optional values).
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| 12 |
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| 13 | =head2 Identity
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| 14 |
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| 15 | "KBKDF" is the name for this implementation; it can be used with the
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| 16 | EVP_KDF_fetch() function.
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| 17 |
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| 18 | =head2 Supported parameters
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| 19 |
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| 20 | The supported parameters are:
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| 21 |
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| 22 | =over 4
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| 23 |
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| 24 | =item "mode" (B<OSSL_KDF_PARAM_MODE>) <UTF8 string>
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| 25 |
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| 26 | The mode parameter determines which flavor of KBKDF to use - currently the
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| 27 | choices are "counter" and "feedback". "counter" is the default, and will be
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| 28 | used if unspecified.
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| 29 |
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| 30 | =item "mac" (B<OSSL_KDF_PARAM_MAC>) <UTF8 string>
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| 31 |
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| 32 | The value is either CMAC, HMAC, KMAC128 or KMAC256.
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| 33 |
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| 34 | =item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
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| 35 |
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| 36 | =item "cipher" (B<OSSL_KDF_PARAM_CIPHER>) <UTF8 string>
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| 37 |
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| 38 | =item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
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| 39 |
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| 40 | =item "key" (B<OSSL_KDF_PARAM_KEY>) <octet string>
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| 41 |
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| 42 | =item "salt" (B<OSSL_KDF_PARAM_SALT>) <octet string>
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| 43 |
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| 44 | =item "info (B<OSSL_KDF_PARAM_INFO>) <octet string>
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| 45 |
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| 46 | =item "seed" (B<OSSL_KDF_PARAM_SEED>) <octet string>
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| 47 |
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| 48 | The seed parameter is unused in counter mode.
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| 49 |
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| 50 | =item "use-l" (B<OSSL_KDF_PARAM_KBKDF_USE_L>) <integer>
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| 51 |
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| 52 | Set to B<0> to disable use of the optional Fixed Input data 'L' (see SP800-108).
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| 53 | The default value of B<1> will be used if unspecified.
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| 54 |
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| 55 | =item "use-separator" (B<OSSL_KDF_PARAM_KBKDF_USE_SEPARATOR>) <integer>
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| 56 |
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| 57 | Set to B<0> to disable use of the optional Fixed Input data 'zero separator'
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| 58 | (see SP800-108) that is placed between the Label and Context.
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| 59 | The default value of B<1> will be used if unspecified.
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| 60 |
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| 61 | =item "r" (B<OSSL_KDF_PARAM_KBKDF_R>) <integer>
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| 62 |
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| 63 | Set the fixed value 'r', indicating the length of the counter in bits.
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| 64 |
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| 65 | Supported values are B<8>, B<16>, B<24>, and B<32>.
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| 66 | The default value of B<32> will be used if unspecified.
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| 67 |
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| 68 | =back
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| 69 |
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| 70 | Depending on whether mac is CMAC or HMAC, either digest or cipher is required
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| 71 | (respectively) and the other is unused. They are unused for KMAC128 and KMAC256.
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| 72 |
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| 73 | The parameters key, salt, info, and seed correspond to KI, Label, Context, and
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| 74 | IV (respectively) in SP800-108. As in that document, salt, info, and seed are
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| 75 | optional and may be omitted.
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| 76 |
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| 77 | "mac", "digest", cipher" and "properties" are described in
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| 78 | L<EVP_KDF(3)/PARAMETERS>.
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| 79 |
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| 80 | =head1 NOTES
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| 81 |
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| 82 | A context for KBKDF can be obtained by calling:
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| 83 |
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| 84 | EVP_KDF *kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL);
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| 85 | EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
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| 86 |
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| 87 | The output length of an KBKDF is specified via the C<keylen>
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| 88 | parameter to the L<EVP_KDF_derive(3)> function.
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| 89 |
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| 90 | Note that currently OpenSSL only implements counter and feedback modes. Other
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| 91 | variants may be supported in the future.
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| 92 |
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| 93 | =head1 EXAMPLES
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| 94 |
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| 95 | This example derives 10 bytes using COUNTER-HMAC-SHA256, with KI "secret",
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| 96 | Label "label", and Context "context".
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| 97 |
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| 98 | EVP_KDF *kdf;
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| 99 | EVP_KDF_CTX *kctx;
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| 100 | unsigned char out[10];
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| 101 | OSSL_PARAM params[6], *p = params;
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| 102 |
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| 103 | kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL);
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| 104 | kctx = EVP_KDF_CTX_new(kdf);
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| 105 | EVP_KDF_free(kdf);
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| 106 |
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| 107 | *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
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| 108 | "SHA2-256", 0);
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| 109 | *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC,
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| 110 | "HMAC", 0);
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| 111 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY,
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| 112 | "secret", strlen("secret"));
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| 113 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
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| 114 | "label", strlen("label"));
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| 115 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
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| 116 | "context", strlen("context"));
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| 117 | *p = OSSL_PARAM_construct_end();
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| 118 | if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0)
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| 119 | error("EVP_KDF_derive");
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| 120 |
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| 121 | EVP_KDF_CTX_free(kctx);
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| 122 |
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| 123 | This example derives 10 bytes using FEEDBACK-CMAC-AES256, with KI "secret",
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| 124 | Label "label", and IV "sixteen bytes iv".
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| 125 |
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| 126 | EVP_KDF *kdf;
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| 127 | EVP_KDF_CTX *kctx;
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| 128 | unsigned char out[10];
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| 129 | OSSL_PARAM params[8], *p = params;
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| 130 | unsigned char *iv = "sixteen bytes iv";
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| 131 |
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| 132 | kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL);
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| 133 | kctx = EVP_KDF_CTX_new(kdf);
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| 134 | EVP_KDF_free(kdf);
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| 135 |
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| 136 | *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_CIPHER, "AES256", 0);
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| 137 | *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC, "CMAC", 0);
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| 138 | *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MODE, "FEEDBACK", 0);
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| 139 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY,
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| 140 | "secret", strlen("secret"));
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| 141 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
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| 142 | "label", strlen("label"));
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| 143 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
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| 144 | "context", strlen("context"));
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| 145 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SEED,
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| 146 | iv, strlen(iv));
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| 147 | *p = OSSL_PARAM_construct_end();
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| 148 | if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0)
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| 149 | error("EVP_KDF_derive");
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| 150 |
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| 151 | EVP_KDF_CTX_free(kctx);
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| 152 |
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| 153 | =head1 CONFORMING TO
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| 154 |
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| 155 | NIST SP800-108, IETF RFC 6803, IETF RFC 8009.
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| 156 |
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| 157 | =head1 SEE ALSO
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| 158 |
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| 159 | L<EVP_KDF(3)>,
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| 160 | L<EVP_KDF_CTX_free(3)>,
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| 161 | L<EVP_KDF_CTX_get_kdf_size(3)>,
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| 162 | L<EVP_KDF_derive(3)>,
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| 163 | L<EVP_KDF(3)/PARAMETERS>
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| 164 |
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| 165 | =head1 HISTORY
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| 166 |
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| 167 | This functionality was added in OpenSSL 3.0.
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| 168 |
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| 169 | Support for KMAC was added in OpenSSL 3.1.
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| 170 |
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| 171 | =head1 COPYRIGHT
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| 172 |
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| 173 | Copyright 2019-2022 The OpenSSL Project Authors. All Rights Reserved.
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| 174 | Copyright 2019 Red Hat, Inc.
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| 175 |
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| 176 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 177 | this file except in compliance with the License. You can obtain a copy
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| 178 | in the file LICENSE in the source distribution or at
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| 179 | L<https://www.openssl.org/source/license.html>.
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| 180 |
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| 181 | =cut
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