EVP_RAND-HASH-DRBG(7SSL)

📦
version 4.0.3 · 13 versions
, in ubuntu stonking

💖 EVP_RAND-HASH-DRBG 💖

okay bestie, welcome to EVP_RAND-HASH-DRBG (that's the 7SSL manual, we're in OpenSSL territory now 🫶). This is the page about The HASH DRBG EVP_RAND implementation — yes, the hash deterministic random bit generator, and yes, it's as iconic as it sounds.

✨ NAME ✨

EVP_RAND-HASH-DRBG — the HASH DRBG EVP_RAND implementation. that's the whole name, she's simple like that 💅

🌸 DESCRIPTION 🌸

Support for the hash deterministic random bit generator comes through the EVP_RAND API. that's the vibe. that's the whole vibe.

🎀 Identity 🎀

"HASH-DRBG" is the name for this implementation — that's what you yell at EVP_RAND_fetch() when you want her. no cap.

💅 Supported parameters 💅

here's the full roster, no skips, every single one:

  • "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>
  • "digest" (OSSL_DRBG_PARAM_DIGEST) <UTF8 string>

These parameters work as described in "PARAMETERS" in EVP_RAND(3).

and two more that are their own little duo:

  • "fips-indicator" (OSSL_DRBG_PARAM_FIPS_APPROVED_INDICATOR) <integer>
  • "digest-check" (OSSL_DRBG_PARAM_FIPS_DIGEST_CHECK) <integer>

These parameters work as described in "PARAMETERS" in provider-rand(7).

🔥 NOTES 🔥

okay listen up, this part matters 👑

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>):

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.

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

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 🌈

the moment you've all been waiting for, a whole serve of code, literally untouched, verbatim, periodt:

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 — she follows the rules, she's a good girl 🎀

🦋 SEE ALSO 🦋

⭐ 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>.

ngl bestie, the original page literally says "complaint manner" — we're keeping it exactly how it's written. no edits, no notes, we don't fix, we just report 🫡

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>.

and that's the whole page, bestie!! ✨🌸 this was EVP_RAND-HASH-DRBG(7SSL) from OpenSSL 4.0.3, dated 2026-09-29 — go forth and generate them bits, you absolute main character 🫶💖🎀

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