NAME

       EVP_RAND-HMAC-DRBG - The HMAC DRBG EVP_RAND implementation

DESCRIPTION

       Support for the HMAC deterministic random bit generator through the EVP_RAND API.

   Identity
       "HMAC-DRBG" is the name for this implementation; it can be used with the EVP_RAND_fetch()
       function.

   Supported parameters
       The supported parameters are:

       "state" (OSSL_RAND_PARAM_STATE) <integer>
       "strength" (OSSL_RAND_PARAM_STRENGTH) <unsigned integer>
       "max_request" (OSSL_RAND_PARAM_MAX_REQUEST) <unsigned integer>
       "reseed_requests" (OSSL_DRBG_PARAM_RESEED_REQUESTS) <unsigned integer>
       "reseed_time_interval" (OSSL_DRBG_PARAM_RESEED_TIME_INTERVAL) <integer>
       "min_entropylen" (OSSL_DRBG_PARAM_MIN_ENTROPYLEN) <unsigned integer>
       "max_entropylen" (OSSL_DRBG_PARAM_MAX_ENTROPYLEN) <unsigned integer>
       "min_noncelen" (OSSL_DRBG_PARAM_MIN_NONCELEN) <unsigned integer>
       "max_noncelen" (OSSL_DRBG_PARAM_MAX_NONCELEN) <unsigned integer>
       "max_perslen" (OSSL_DRBG_PARAM_MAX_PERSLEN) <unsigned integer>
       "max_adinlen" (OSSL_DRBG_PARAM_MAX_ADINLEN) <unsigned integer>
       "reseed_counter" (OSSL_DRBG_PARAM_RESEED_COUNTER) <unsigned integer>
       "properties" (OSSL_DRBG_PARAM_PROPERTIES) <UTF8 string>
       "mac" (OSSL_DRBG_PARAM_MAC) <UTF8 string>
       "digest" (OSSL_DRBG_PARAM_DIGEST) <UTF8 string>
           These parameters work as described in "PARAMETERS" in EVP_RAND(3).

NOTES

       When using the FIPS provider, only these digests are permitted (as per FIPS 140-3 IG D.R
       <https://csrc.nist.gov/CSRC/media/Projects/cryptographic-module-validation-
       program/documents/fips%20140-3/FIPS%20140-3%20IG.pdf>):

       SHA-1
       SHA2-256
       SHA2-512
       SHA3-256
       SHA3-512

       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);

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);

CONFORMING TO

       NIST SP 800-90A and SP 800-90B

SEE ALSO

       EVP_RAND(3), "PARAMETERS" in EVP_RAND(3), openssl-fipsinstall(1)

HISTORY

       OpenSSL 3.1.1 introduced the -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 FIPS 140-3 IG D.R
       <https://csrc.nist.gov/CSRC/media/Projects/cryptographic-module-validation-
       program/documents/fips%20140-3/FIPS%20140-3%20IG.pdf>).

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 <https://www.openssl.org/source/license.html>.