xref: /openssl/doc/man7/EVP_RAND-CTR-DRBG.pod (revision 0a7528cc) 
1=pod
2
3=head1 NAME
4
5EVP_RAND-CTR-DRBG - The CTR DRBG EVP_RAND implementation
6
7=head1 DESCRIPTION
8
9Support for the counter deterministic random bit generator through the
10B<EVP_RAND> API.
11
12=head2 Identity
13
14"CTR-DRBG" is the name for this implementation; it can be used with the
15EVP_RAND_fetch() function.
16
17=head2 Supported parameters
18
19The 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 "max_request" (B<OSSL_RAND_PARAM_MAX_REQUEST>) <unsigned integer>
28
29=item "reseed_requests" (B<OSSL_DRBG_PARAM_RESEED_REQUESTS>) <unsigned integer>
30
31=item "reseed_time_interval" (B<OSSL_DRBG_PARAM_RESEED_TIME_INTERVAL>) <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_COUNTER>) <unsigned integer>
46
47=item "properties" (B<OSSL_DRBG_PARAM_PROPERTIES>) <UTF8 string>
48
49=item "cipher" (B<OSSL_DRBG_PARAM_CIPHER>) <UTF8 string>
50
51These parameters work as described in L<EVP_RAND(3)/PARAMETERS>.
52
53=item "use_derivation_function" (B<OSSL_DRBG_PARAM_USE_DF>) <integer>
54
55This Boolean indicates if a derivation function should be used or not.
56A nonzero value (the default) uses the derivation function.  A zero value
57does not.
58
59=back
60
61=head1 NOTES
62
63A context for CTR DRBG can be obtained by calling:
64
65 EVP_RAND *rand = EVP_RAND_fetch(NULL, "CTR-DRBG", NULL);
66 EVP_RAND_CTX *rctx = EVP_RAND_CTX_new(rand, NULL);
67
68=head1 EXAMPLES
69
70 EVP_RAND *rand;
71 EVP_RAND_CTX *rctx;
72 unsigned char bytes[100];
73 OSSL_PARAM params[2], *p = params;
74 unsigned int strength = 128;
75
76 rand = EVP_RAND_fetch(NULL, "CTR-DRBG", NULL);
77 rctx = EVP_RAND_CTX_new(rand, NULL);
78 EVP_RAND_free(rand);
79
80 *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_CIPHER,
81                                         SN_aes_256_ctr, 0);
82 *p = OSSL_PARAM_construct_end();
83 EVP_RAND_instantiate(rctx, strength, 0, NULL, 0, params);
84
85 EVP_RAND_generate(rctx, bytes, sizeof(bytes), strength, 0, NULL, 0);
86
87 EVP_RAND_CTX_free(rctx);
88
89=head1 CONFORMING TO
90
91NIST SP 800-90A and SP 800-90B
92
93=head1 SEE ALSO
94
95L<EVP_RAND(3)>,
96L<EVP_RAND(3)/PARAMETERS>
97
98=head1 COPYRIGHT
99
100Copyright 2020-2021 The OpenSSL Project Authors. All Rights Reserved.
101
102Licensed under the Apache License 2.0 (the "License").  You may not use
103this file except in compliance with the License.  You can obtain a copy
104in the file LICENSE in the source distribution or at
105L<https://www.openssl.org/source/license.html>.
106
107=cut
108