doc/man7/EVP_KDF-KB.pod

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