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 68The default CTR-DRBG implementation attempts to fetch the required internal 69algorithms from the provider they are built into (eg the default provider) 70regardless of the properties provided. Should the provider not implement 71the required algorithms then properties will be used to find a different 72implementation. 73 74=head1 EXAMPLES 75 76 EVP_RAND *rand; 77 EVP_RAND_CTX *rctx; 78 unsigned char bytes[100]; 79 OSSL_PARAM params[2], *p = params; 80 unsigned int strength = 128; 81 82 rand = EVP_RAND_fetch(NULL, "CTR-DRBG", NULL); 83 rctx = EVP_RAND_CTX_new(rand, NULL); 84 EVP_RAND_free(rand); 85 86 *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_CIPHER, 87 SN_aes_256_ctr, 0); 88 *p = OSSL_PARAM_construct_end(); 89 EVP_RAND_instantiate(rctx, strength, 0, NULL, 0, params); 90 91 EVP_RAND_generate(rctx, bytes, sizeof(bytes), strength, 0, NULL, 0); 92 93 EVP_RAND_CTX_free(rctx); 94 95=head1 CONFORMING TO 96 97NIST SP 800-90A and SP 800-90B 98 99=head1 SEE ALSO 100 101L<EVP_RAND(3)>, 102L<EVP_RAND(3)/PARAMETERS> 103 104=head1 COPYRIGHT 105 106Copyright 2020-2025 The OpenSSL Project Authors. All Rights Reserved. 107 108Licensed under the Apache License 2.0 (the "License"). You may not use 109this file except in compliance with the License. You can obtain a copy 110in the file LICENSE in the source distribution or at 111L<https://www.openssl.org/source/license.html>. 112 113=cut 114