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EVP_RAND-HMAC-DRBG(7)               OpenSSL              EVP_RAND-HMAC-DRBG(7)



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
       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);

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)

COPYRIGHT
       Copyright 2020-2021 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>.



3.0.12                            2023-05-07             EVP_RAND-HMAC-DRBG(7)