evp_rand: documentation
[openssl.git] / doc / man7 / EVP_RAND-HASH-DRBG.pod
1 =pod
2
3 =head1 NAME
4
5 EVP_RAND-HASH-DRBG - The HASH DRBG EVP_RAND implementation
6
7 =head1 DESCRIPTION
8
9 Support for the hash deterministic random bit generator through the
10 B<EVP_RAND> API.
11
12 =head2 Identity
13
14 "HASH-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 "digest" (B<OSSL_DRBG_PARAM_DIGEST>) <UTF8 string>
50
51 These parameters work as described in L<EVP_RAND(3)/PARAMETERS>.
52
53 =back
54
55 =head1 NOTES
56
57 A context for HASH DRBG can be obtained by calling:
58
59  EVP_RAND *rand = EVP_RAND_fetch(NULL, "HASH-DRBG", NULL);
60  EVP_RAND_CTX *rctx = EVP_RAND_CTX_new(rand);
61
62 =head1 EXAMPLES
63
64  EVP_RAND *rand;
65  EVP_RAND_CTX *rctx;
66  unsigned char bytes[100];
67  OSSL_PARAM params[2], *p = params;
68  unsigned int strength = 128;
69
70  rand = EVP_RAND_fetch(NULL, "HASH-DRBG", NULL);
71  rctx = EVP_RAND_CTX_new(rand, NULL);
72  EVP_RAND_free(rand);
73
74  *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_DIGEST, SN_sha512, 0);
75  *p = OSSL_PARAM_construct_end();
76  EVP_RAND_set_ctx_params(rctx, params);
77
78  EVP_RAND_generate(rctx, bytes, sizeof(bytes), strength, 0, NULL, 0);
79
80  EVP_RAND_CTX_free(rctx);
81
82 =head1 CONFORMING TO
83
84 NIST SP 800-90A and SP 800-90B
85
86 =head1 SEE ALSO
87
88 L<EVP_RAND(3)>,
89 L<EVP_RAND(3)/PARAMETERS>
90
91 =head1 COPYRIGHT
92
93 Copyright 2020 The OpenSSL Project Authors. All Rights Reserved.
94
95 Licensed under the Apache License 2.0 (the "License").  You may not use
96 this file except in compliance with the License.  You can obtain a copy
97 in the file LICENSE in the source distribution or at
98 L<https://www.openssl.org/source/license.html>.
99
100 =cut