[KDF] Add feedback-mode and CMAC support to KBKDF
[openssl.git] / 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                                          "SHA256", 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                                           "context", strlen("context"));
90  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
91                                           "label", strlen("label"));
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                                           "context", strlen("context"));
120  *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
121                                           "label", strlen("label"));
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_new_id(3)>,
140 L<EVP_KDF_CTX_free(3)>,
141 L<EVP_KDF_ctrl(3)>,
142 L<EVP_KDF_size(3)>,
143 L<EVP_KDF_derive(3)>,
144 L<EVP_KDF(3)/PARAMETERS>
145
146 =head1 HISTORY
147
148 This functionality was added to OpenSSL 3.0.
149
150 =head1 COPYRIGHT
151
152 Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
153 Copyright 2019 Red Hat, Inc.
154
155 Licensed under the Apache License 2.0 (the "License").  You may not use
156 this file except in compliance with the License.  You can obtain a copy
157 in the file LICENSE in the source distribution or at
158 L<https://www.openssl.org/source/license.html>.
159
160 =cut