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 "mode" (B<OSSL_KDF_PARAM_MODE>) <UTF8 string>
  25
  26 The mode parameter determines which flavor of KBKDF to use - currently the
  27 choices are "counter" and "feedback". "counter" is the default, and will be
  28 used if unspecified.
  29
  30 =item "mac" (B<OSSL_KDF_PARAM_MAC>) <UTF8 string>
  31
  32 The value is either CMAC or HMAC.
  33
  34 =item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
  35
  36 =item "cipher" (B<OSSL_KDF_PARAM_CIPHER>) <UTF8 string>
  37
  38 =item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
  39
  40 =item "key" (B<OSSL_KDF_PARAM_KEY>) <octet string>
  41
  42 =item "salt" (B<OSSL_KDF_PARAM_SALT>) <octet string>
  43
  44 =item "info (B<OSSL_KDF_PARAM_INFO>) <octet string>
  45
  46 =item "seed" (B<OSSL_KDF_PARAM_SEED>) <octet string>
  47
  48 The seed parameter is unused in counter mode.
  49
  50 =item "use-l" (B<OSSL_KDF_PARAM_KBKDF_USE_L>) <int>
  51
  52 Set to B<0> to disable use of the optional Fixed Input data 'L' (see SP800-108).
  53 The default value of B<1> will be used if unspecified.
  54
  55 =item "use-separator" (B<OSSL_KDF_PARAM_KBKDF_USE_SEPARATOR>) <int>
  56
  57 Set to B<0> to disable use of the optional Fixed Input data 'zero separator'
  58 (see SP800-108) that is placed between the Label and Context.
  59 The default value of B<1> will be used if unspecified.
  60
  61 =back
  62
  63 Depending on whether mac is CMAC or HMAC, either digest or cipher is required
  64 (respectively) and the other is unused.
  65
  66 The parameters key, salt, info, and seed correspond to KI, Label, Context, and
  67 IV (respectively) in SP800-108.  As in that document, salt, info, and seed are
  68 optional and may be omitted.
  69
  70 "mac", "digest", cipher" and "properties" are described in
  71 L<EVP_KDF(3)/PARAMETERS>.
  72
  73 =head1 NOTES
  74
  75 A context for KBKDF can be obtained by calling:
  76
  77  EVP_KDF *kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL);
  78  EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
  79
  80 The output length of an KBKDF is specified via the C<keylen>
  81 parameter to the L<EVP_KDF_derive(3)> function.
  82
  83 Note that currently OpenSSL only implements counter and feedback modes.  Other
  84 variants may be supported in the future.
  85
  86 =head1 EXAMPLES
  87
  88 This example derives 10 bytes using COUNTER-HMAC-SHA256, with KI "secret",
  89 Label "label", and Context "context".
  90
  91  EVP_KDF *kdf;
  92  EVP_KDF_CTX *kctx;
  93  unsigned char out[10];
  94  OSSL_PARAM params[6], *p = params;
  95
  96  kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL);
  97  kctx = EVP_KDF_CTX_new(kdf);
  98  EVP_KDF_free(kdf);
  99
 100  *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
 101                                          "SHA2-256", 0);
 102  *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC,
 103                                          "HMAC", 0);
 104  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY,
 105                                           "secret", strlen("secret"));
 106  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
 107                                           "label", strlen("label"));
 108  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
 109                                           "context", strlen("context"));
 110  *p = OSSL_PARAM_construct_end();
 111  if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0)
 112      error("EVP_KDF_derive");
 113
 114  EVP_KDF_CTX_free(kctx);
 115
 116 This example derives 10 bytes using FEEDBACK-CMAC-AES256, with KI "secret",
 117 Label "label", and IV "sixteen bytes iv".
 118
 119  EVP_KDF *kdf;
 120  EVP_KDF_CTX *kctx;
 121  unsigned char out[10];
 122  OSSL_PARAM params[8], *p = params;
 123  unsigned char *iv = "sixteen bytes iv";
 124
 125  kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL);
 126  kctx = EVP_KDF_CTX_new(kdf);
 127  EVP_KDF_free(kdf);
 128
 129  *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_CIPHER, "AES256", 0);
 130  *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC, "CMAC", 0);
 131  *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MODE, "FEEDBACK", 0);
 132  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY,
 133                                           "secret", strlen("secret"));
 134  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
 135                                           "label", strlen("label"));
 136  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
 137                                           "context", strlen("context"));
 138  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SEED,
 139                                           iv, strlen(iv));
 140  *p = OSSL_PARAM_construct_end();
 141  if (EVP_KDF_CTX_set_params(kctx, params) <= 0)
 142      error("EVP_KDF_CTX_set_params");
 143  else if (EVP_KDF_derive(kctx, out, sizeof(out)) <= 0)
 144      error("EVP_KDF_derive");
 145
 146  EVP_KDF_CTX_free(kctx);
 147
 148 =head1 CONFORMING TO
 149
 150 NIST SP800-108, IETF RFC 6803, IETF RFC 8009.
 151
 152 =head1 SEE ALSO
 153
 154 L<EVP_KDF(3)>,
 155 L<EVP_KDF_CTX_free(3)>,
 156 L<EVP_KDF_CTX_get_kdf_size(3)>,
 157 L<EVP_KDF_derive(3)>,
 158 L<EVP_KDF(3)/PARAMETERS>
 159
 160 =head1 HISTORY
 161
 162 This functionality was added to OpenSSL 3.0.
 163
 164 =head1 COPYRIGHT
 165
 166 Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved.
 167 Copyright 2019 Red Hat, Inc.
 168
 169 Licensed under the Apache License 2.0 (the "License").  You may not use
 170 this file except in compliance with the License.  You can obtain a copy
 171 in the file LICENSE in the source distribution or at
 172 L<https://www.openssl.org/source/license.html>.
 173
 174 =cut