evp_rand: documentation
[openssl.git] / doc / man7 / EVP_RAND-HMAC-DRBG.pod
1 =pod
2
3 =head1 NAME
4
5 EVP_RAND-HMAC-DRBG - The HMAC DRBG EVP_RAND implementation
6
7 =head1 DESCRIPTION
8
9 Support for the HMAC deterministic random bit generator through the
10 B<EVP_RAND> API.
11
12 =head2 Identity
13
14 "HMAC-DRBG" is the name for this implementation; it can be used with the
15 EVP_RAND_fetch() function.
16
17 =head2 Supported parameters
18
19 The supported parameters are:
20
21 =over 4
22
23 =item "state" (B<OSSL_RAND_PARAM_STATE>) <integer>
24
25 =item "strength" (B<OSSL_RAND_PARAM_STRENGTH>) <unsigned integer>
26
27 =item "reseed_requests" (B<OSSL_DRBG_PARAM_RESEED_REQUESTS>) <unsigned integer>
28
29 =item "reseed_time_interval" (B<OSSL_DRBG_PARAM_RESEED_TIME_INTERVAL>) <integer>
30
31 =item "max_request" (B<OSSL_DRBG_PARAM_MAX_REQUEST>) <unsigned integer>
32
33 =item "min_entropylen" (B<OSSL_DRBG_PARAM_MIN_ENTROPYLEN>) <unsigned integer>
34
35 =item "max_entropylen" (B<OSSL_DRBG_PARAM_MAX_ENTROPYLEN>) <unsigned integer>
36
37 =item "min_noncelen" (B<OSSL_DRBG_PARAM_MIN_NONCELEN>) <unsigned integer>
38
39 =item "max_noncelen" (B<OSSL_DRBG_PARAM_MAX_NONCELEN>) <unsigned integer>
40
41 =item "max_perslen" (B<OSSL_DRBG_PARAM_MAX_PERSLEN>) <unsigned integer>
42
43 =item "max_adinlen" (B<OSSL_DRBG_PARAM_MAX_ADINLEN>) <unsigned integer>
44
45 =item "reseed_counter" (B<OSSL_DRBG_PARAM_RESEED_CTR>) <unsigned integer>
46
47 =item "properties" (B<OSSL_DRBG_PARAM_PROPERTIES>) <UTF8 string>
48
49 =item "mac" (B<OSSL_DRBG_PARAM_MAC>) <UTF8 string>
50
51 =item "digest" (B<OSSL_DRBG_PARAM_DIGEST>) <UTF8 string>
52
53 These parameters work as described in L<EVP_RAND(3)/PARAMETERS>.
54
55 =back
56
57 =head1 NOTES
58
59 A context for HMAC DRBG can be obtained by calling:
60
61  EVP_RAND *rand = EVP_RAND_fetch(NULL, "HMAC-DRBG", NULL);
62  EVP_RAND_CTX *rctx = EVP_RAND_CTX_new(rand);
63
64 =head1 EXAMPLES
65
66  EVP_RAND *rand;
67  EVP_RAND_CTX *rctx;
68  unsigned char bytes[100];
69  OSSL_PARAM params[3], *p = params;
70  unsigned int strength = 128;
71
72  rand = EVP_RAND_fetch(NULL, "HMAC-DRBG", NULL);
73  rctx = EVP_RAND_CTX_new(rand, NULL);
74  EVP_RAND_free(rand);
75
76  *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_MAC, SN_hmac, 0);
77  *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_DIGEST, SN_sha256, 0);
78  *p = OSSL_PARAM_construct_end();
79  EVP_RAND_set_ctx_params(rctx, params);
80
81  EVP_RAND_generate(rctx, bytes, sizeof(bytes), strength, 0, NULL, 0);
82
83  EVP_RAND_CTX_free(rctx);
84
85 =head1 CONFORMING TO
86
87 NIST SP 800-90A and SP 800-90B
88
89 =head1 SEE ALSO
90
91 L<EVP_RAND(3)>,
92 L<EVP_RAND(3)/PARAMETERS>
93
94 =head1 COPYRIGHT
95
96 Copyright 2020 The OpenSSL Project Authors. All Rights Reserved.
97
98 Licensed under the Apache License 2.0 (the "License").  You may not use
99 this file except in compliance with the License.  You can obtain a copy
100 in the file LICENSE in the source distribution or at
101 L<https://www.openssl.org/source/license.html>.
102
103 =cut