EVP_RAND-HASH-DRBG(7ossl)

📦
version 3.5.9 · 8 versions
, in alpine 3.23, alpine 3.24

💖 EVP_RAND-HASH-DRBG(7ossl) 💖

okay so this is the OpenSSL manual page for the HASH DRBG situation, and bestie, it's giving cryptography core 🎀 (the manual name is EVP_RAND-HASH-DRBG and it lives in section 7ossl, iykyk)

✨ NAME ✨

EVP_RAND-HASH-DRBG — the HASH DRBG EVP_RAND implementation, periodt 💅

🌸 DESCRIPTION 🌸

So basically this is the support for the hash deterministic random bit generator that you get to use through the EVP_RAND API. That's it, that's the vibe 🦋

🪪 Identity 🪪

"HASH-DRBG" is literally the name of this implementation, no cap. You can use it with the EVP_RAND_fetch() function, bestie 🔥

🔧 Supported parameters 🔧

Here's the whole roster of supported parameters — she's thorough 👑

  • "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 exactly as described in "PARAMETERS" in EVP_RAND(3), fr fr 🫶

And also these two cuties:

  • "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 important part, pay attention bestie 🙈

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. But lowkey, 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

✨ And you can get yourself a context for HASH DRBG by calling this:

EVP_RAND *rand = EVP_RAND_fetch(NULL, "HASH-DRBG", NULL);
EVP_RAND_CTX *rctx = EVP_RAND_CTX_new(rand, NULL);

🎀 EXAMPLES 🎀

here's the whole glow-up in action, slay 💅

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's certified, she's legit, she's iconic 👑

🦋 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 complaint manner. For details, refer to FIPS 140-3 IG D.R here: https://csrc.nist.gov/CSRC/media/Projects/cryptographic-module-validation-program/documents/fips%20140-3/FIPS%20140-3%20IG.pdf 📚

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 🫶

aaaand that's the whole page! version 3.5.9, dated 2026-09-29 — signed, sealed, delivered by your fave EVP_RAND-HASH-DRBG(7ossl) girly 💖✨🎀

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