=pod =head1 NAME EVP_RAND-HMAC-DRBG - The HMAC DRBG EVP_RAND implementation =head1 DESCRIPTION Support for the HMAC deterministic random bit generator through the B API. =head2 Identity "HMAC-DRBG" is the name for this implementation; it can be used with the EVP_RAND_fetch() function. =head2 Supported parameters The supported parameters are: =over 4 =item "state" (B) =item "strength" (B) =item "max_request" (B) =item "reseed_requests" (B) =item "reseed_time_interval" (B) =item "min_entropylen" (B) =item "max_entropylen" (B) =item "min_noncelen" (B) =item "max_noncelen" (B) =item "max_perslen" (B) =item "max_adinlen" (B) =item "reseed_counter" (B) =item "properties" (B) =item "mac" (B) =item "digest" (B) These parameters work as described in L. =back =head1 NOTES When using the FIPS provider, only these digests are permitted (as per L): =over 4 =item SHA-1 =item SHA2-256 =item SHA2-512 =item SHA3-256 =item SHA3-512 =back A context for HMAC DRBG can be obtained by calling: EVP_RAND *rand = EVP_RAND_fetch(NULL, "HMAC-DRBG", NULL); EVP_RAND_CTX *rctx = EVP_RAND_CTX_new(rand, NULL); =head1 EXAMPLES EVP_RAND *rand; EVP_RAND_CTX *rctx; unsigned char bytes[100]; OSSL_PARAM params[3], *p = params; unsigned int strength = 128; rand = EVP_RAND_fetch(NULL, "HMAC-DRBG", NULL); rctx = EVP_RAND_CTX_new(rand, NULL); EVP_RAND_free(rand); *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_MAC, SN_hmac, 0); *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_DIGEST, SN_sha256, 0); *p = OSSL_PARAM_construct_end(); EVP_RAND_instantiate(rctx, strength, 0, NULL, 0, params); EVP_RAND_generate(rctx, bytes, sizeof(bytes), strength, 0, NULL, 0); EVP_RAND_CTX_free(rctx); =head1 CONFORMING TO NIST SP 800-90A and SP 800-90B =head1 SEE ALSO L, L, L =head1 HISTORY OpenSSL 3.1.1 introduced the B<-no_drbg_truncated_digests> option to fipsinstall which restricts the permitted digests when using the FIPS provider in a complaint manner. For details refer to L). =head1 COPYRIGHT Copyright 2020-2023 The OpenSSL Project Authors. All Rights Reserved. Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at L. =cut