EVP_RAND-HASH-DRBG(7ossl)

💖 EVP_RAND-HASH-DRBG 💖

okay bestie, welcome to the 7ossl manual page for EVP_RAND-HASH-DRBG — literally the hash deterministic random bit generator, but make it main character energy through the EVP_RAND API. ✨

🌸 NAME 🌸

EVP_RAND-HASH-DRBG — The HASH DRBG EVP_RAND implementation. That's the name, that's the vibe, no cap.

🦋 DESCRIPTION 🦋

Support for the hash deterministic random bit generator through the EVP_RAND API. slay.

🪪 Identity 🪪

"HASH-DRBG" is the name for this implementation; you can use it with the EVP_RAND_fetch() function. iykyk 💅

🎀 Supported parameters 🎀

The supported parameters are:

These all work exactly as described in "PARAMETERS" in EVP_RAND(3):

• "state" (OSSL_RAND_PARAM_STATE) <integer> — the state parameter, doing its state parameter thing.
• "strength" (OSSL_RAND_PARAM_STRENGTH) <unsigned integer> — the strength parameter.
• "max_request" (OSSL_RAND_PARAM_MAX_REQUEST) <unsigned integer> — the max request parameter.
• "reseed_requests" (OSSL_DRBG_PARAM_RESEED_REQUESTS) <unsigned integer> — the reseed requests parameter.
• "reseed_time_interval" (OSSL_DRBG_PARAM_RESEED_TIME_INTERVAL) <integer> — the reseed time interval parameter.
• "min_entropylen" (OSSL_DRBG_PARAM_MIN_ENTROPYLEN) <unsigned integer> — the minimum entropy length parameter.
• "max_entropylen" (OSSL_DRBG_PARAM_MAX_ENTROPYLEN) <unsigned integer> — the maximum entropy length parameter.
• "min_noncelen" (OSSL_DRBG_PARAM_MIN_NONCELEN) <unsigned integer> — the minimum nonce length parameter.
• "max_noncelen" (OSSL_DRBG_PARAM_MAX_NONCELEN) <unsigned integer> — the maximum nonce length parameter.
• "max_perslen" (OSSL_DRBG_PARAM_MAX_PERSLEN) <unsigned integer> — the maximum personalization string length parameter.
• "max_adinlen" (OSSL_DRBG_PARAM_MAX_ADINLEN) <unsigned integer> — the maximum additional input length parameter.
• "reseed_counter" (OSSL_DRBG_PARAM_RESEED_COUNTER) <unsigned integer> — the reseed counter parameter.
• "properties" (OSSL_DRBG_PARAM_PROPERTIES) <UTF8 string> — the properties parameter.
• "digest" (OSSL_DRBG_PARAM_DIGEST) <UTF8 string> — the digest parameter.

And these two work exactly as described in "PARAMETERS" in provider-rand(7):

• "fips-indicator" (OSSL_DRBG_PARAM_FIPS_APPROVED_INDICATOR) <integer> — the FIPS approved indicator parameter.
• "digest-check" (OSSL_DRBG_PARAM_FIPS_DIGEST_CHECK) <integer> — the FIPS digest check parameter.

👑 NOTES 👑

When the FIPS provider is installed using the -no_drbg_truncated_digests option to fipsinstall, 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

Also, heads up bestie: the default HASH-DRBG implementation attempts to fetch the required internal algorithms from the provider they are built into (eg the default provider) regardless of the properties provided. Should the provider not implement the required algorithms then properties will be used to find a different implementation. that's the whole rule, fr fr 🫶

A context for HASH DRBG can be obtained by calling:

EVP_RAND *rand = EVP_RAND_fetch(NULL, "HASH-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[2], *p = params;
unsigned int strength = 128;

rand = EVP_RAND_fetch(NULL, "HASH-DRBG", NULL);
rctx = EVP_RAND_CTX_new(rand, NULL);
EVP_RAND_free(rand);

*p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_DIGEST, SN_sha512, 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. standards girlie behavior 💅

🔥 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 compliant 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. the lore is real 📜

🎀 COPYRIGHT 🎀

Copyright 2020-2025 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.

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mwah 💋 — OpenSSL 3.5.0, dated 2026-09-25, manual EVP_RAND-HASH-DRBG(7ossl). bye bestie 🫶