doc/man7/EVP_KDF-SS.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 EVP_KDF-SS - The Single Step / One Step EVP_KDF implementation
   6
   7 =head1 DESCRIPTION
   8
   9 The EVP_KDF-SS algorithm implements the Single Step key derivation function (SSKDF).
  10 SSKDF derives a key using input such as a shared secret key (that was generated
  11 during the execution of a key establishment scheme) and fixedinfo.
  12 SSKDF is also informally referred to as 'Concat KDF'.
  13
  14 =head2 Auxiliary function
  15
  16 The implementation uses a selectable auxiliary function H, which can be one of:
  17
  18 =over 4
  19
  20 =item B<H(x) = hash(x, digest=md)>
  21
  22 =item B<H(x) = HMAC_hash(x, key=salt, digest=md)>
  23
  24 =item B<H(x) = KMACxxx(x, key=salt, custom="KDF", outlen=mac_size)>
  25
  26 =back
  27
  28 Both the HMAC and KMAC implementations set the key using the 'salt' value.
  29 The hash and HMAC also require the digest to be set.
  30
  31 =head2 Identity
  32
  33 "SSKDF" is the name for this implementation; it
  34 can be used with the EVP_KDF_fetch() function.
  35
  36 =head2 Supported parameters
  37
  38 The supported parameters are:
  39
  40 =over 4
  41
  42 =item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
  43
  44 =item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
  45
  46 =item "mac" (B<OSSL_KDF_PARAM_MAC>) <UTF8 string>
  47
  48 =item "maclen" (B<OSSL_KDF_PARAM_MAC_SIZE>) <unsigned integer>
  49
  50 =item "salt" (B<OSSL_KDF_PARAM_SALT>) <octet string>
  51
  52 These parameters work as described in L<EVP_KDF(3)/PARAMETERS>.
  53
  54 =item "key" (B<EVP_KDF_CTRL_SET_KEY>) <octet string>
  55
  56 This parameter set the shared secret that is used for key derivation.
  57
  58 =item "info" (B<OSSL_KDF_PARAM_INFO>) <octet string>
  59
  60 This parameter sets an optional value for fixedinfo, also known as otherinfo.
  61
  62 =back
  63
  64 =head1 NOTES
  65
  66 A context for SSKDF can be obtained by calling:
  67
  68  EVP_KDF *kdf = EVP_KDF_fetch(NULL, "SSKDF", NULL);
  69  EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
  70
  71 The output length of an SSKDF is specified via the I<keylen>
  72 parameter to the L<EVP_KDF_derive(3)> function.
  73
  74 =head1 EXAMPLES
  75
  76 This example derives 10 bytes using H(x) = SHA-256, with the secret key "secret"
  77 and fixedinfo value "label":
  78
  79  EVP_KDF *kdf;
  80  EVP_KDF_CTX *kctx;
  81  unsigned char out[10];
  82  OSSL_PARAM params[4], *p = params;
  83
  84  kdf = EVP_KDF_fetch(NULL, "SSKDF", NULL);
  85  kctx = EVP_KDF_CTX_new(kdf);
  86  EVP_KDF_free(kdf);
  87
  88  *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
  89                                          SN_sha256, strlen(SN_sha256));
  90  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY,
  91                                           "secret", (size_t)6);
  92  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
  93                                           "label", (size_t)5);
  94  *p = OSSL_PARAM_construct_end();
  95  if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) {
  96      error("EVP_KDF_derive");
  97  }
  98
  99  EVP_KDF_CTX_free(kctx);
 100
 101 This example derives 10 bytes using H(x) = HMAC(SHA-256), with the secret key "secret",
 102 fixedinfo value "label" and salt "salt":
 103
 104  EVP_KDF *kdf;
 105  EVP_KDF_CTX *kctx;
 106  unsigned char out[10];
 107  OSSL_PARAM params[6], *p = params;
 108
 109  kdf = EVP_KDF_fetch(NULL, "SSKDF", NULL);
 110  kctx = EVP_KDF_CTX_new(kdf);
 111  EVP_KDF_free(kdf);
 112
 113  *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC,
 114                                          SN_hmac, strlen(SN_hmac));
 115  *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
 116                                          SN_sha256, strlen(SN_sha256));
 117  *p++ = OSSL_PARAM_construct_octet_string(EVP_KDF_CTRL_SET_KEY,
 118                                           "secret", (size_t)6);
 119  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
 120                                           "label", (size_t)5);
 121  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
 122                                           "salt", (size_t)4);
 123  *p = OSSL_PARAM_construct_end();
 124  if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) {
 125      error("EVP_KDF_derive");
 126  }
 127
 128  EVP_KDF_CTX_free(kctx);
 129
 130 This example derives 10 bytes using H(x) = KMAC128(x,salt,outlen), with the secret key "secret"
 131 fixedinfo value "label", salt of "salt" and KMAC outlen of 20:
 132
 133  EVP_KDF *kdf;
 134  EVP_KDF_CTX *kctx;
 135  unsigned char out[10];
 136  OSSL_PARAM params[7], *p = params;
 137
 138  kdf = EVP_KDF_fetch(NULL, "SSKDF", NULL);
 139  kctx = EVP_KDF_CTX_new(kdf);
 140  EVP_KDF_free(kdf);
 141
 142  *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC,
 143                                          SN_kmac128, strlen(SN_kmac128));
 144  *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
 145                                          SN_sha256, strlen(SN_sha256));
 146  *p++ = OSSL_PARAM_construct_octet_string(EVP_KDF_CTRL_SET_KEY,
 147                                           "secret", (size_t)6);
 148  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
 149                                           "label", (size_t)5);
 150  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
 151                                           "salt", (size_t)4);
 152  *p++ = OSSL_PARAM_construct_size_t(OSSL_KDF_PARAM_MAC_SIZE, (size_t)20);
 153  *p = OSSL_PARAM_construct_end();
 154  if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0) {
 155      error("EVP_KDF_derive");
 156  }
 157
 158  EVP_KDF_CTX_free(kctx);
 159
 160 =head1 CONFORMING TO
 161
 162 NIST SP800-56Cr1.
 163
 164 =head1 SEE ALSO
 165
 166 L<EVP_KDF(3)>,
 167 L<EVP_KDF_CTX_new(3)>,
 168 L<EVP_KDF_CTX_free(3)>,
 169 L<EVP_KDF_CTX_set_params(3)>,
 170 L<EVP_KDF_CTX_get_kdf_size(3)>,
 171 L<EVP_KDF_derive(3)>,
 172 L<EVP_KDF(3)/PARAMETERS>
 173
 174 =head1 HISTORY
 175
 176 This functionality was added to OpenSSL 3.0.
 177
 178 =head1 COPYRIGHT
 179
 180 Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved.  Copyright
 181 (c) 2019, Oracle and/or its affiliates.  All rights reserved.
 182
 183 Licensed under the Apache License 2.0 (the "License").  You may not use
 184 this file except in compliance with the License.  You can obtain a copy
 185 in the file LICENSE in the source distribution or at
 186 L<https://www.openssl.org/source/license.html>.
 187
 188 =cut