DSA_GENERATE_PARAMETERS(3ossl)

📦
version 3.5.9 · 8 versions
, in fedora 43, fedora 44

💖 DSA_GENERATE_PARAMETERS 💖

okay bestie, welcome to DSA_GENERATE_PARAMETERS(3ossl) — it's an OpenSSL manual page, and yes, the whole thing is lowkey a vintage situation because literally every function on here is deprecated. we're touring the museum today 🏛️✨

✨ NAME ✨

DSA_generate_parameters_ex, DSA_generate_parameters — they generate DSA parameters, that's the whole job 🎀

🌸 SYNOPSIS 🌸

first up, the include, obviously:

#include <openssl/dsa.h>

the first one (deprecated since OpenSSL 3.0, bestie)

so the following functions have been deprecated since OpenSSL 3.0, and you can hide them entirely by defining OPENSSL_API_COMPAT with a suitable version value — go read openssl_user_macros(7) for the deets:

int DSA_generate_parameters_ex(DSA *dsa, int bits,
                               const unsigned char *seed, int seed_len,
                               int *counter_ret, unsigned long *h_ret,
                               BN_GENCB *cb);

the second one (deprecated since OpenSSL 0.9.8, yes really)

the following functions have been deprecated since OpenSSL 0.9.8, and same deal, they can be hidden entirely by defining OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7):

DSA *DSA_generate_parameters(int bits, unsigned char *seed, int seed_len,
                             int *counter_ret, unsigned long *h_ret,
                             void (*callback)(int, int, void *), void *cb_arg);

💅 DESCRIPTION 💅

🚨 real talk first: ALL of the functions described on this page are deprecated. every single one. applications should instead use EVP_PKEY_paramgen_init(3) and EVP_PKEY_keygen(3) as described in EVP_PKEY-DSA(7). that's the glow-up, periodt.

okay so DSA_generate_parameters_ex() generates primes p and q and a generator g for use in the DSA, and stores the result in dsa. iconic math behavior 🧚

bits is the length of the prime p to be generated. and here's the tea on q:

  • for lengths under 2048 bits, the length of q is 160 bits 🍓
  • for lengths greater than or equal to 2048 bits, the length of q is set to 256 bits 💜

if seed is NULL, the primes will be generated at random — chaos mode, we love her 🎲. but if seed_len is less than the length of q, an error is returned. not negotiable, sorry bestie 😭

DSA_generate_parameters_ex() places the iteration count in *counter_ret and a counter used for finding a generator in *h_ret — unless those are NULL, in which case she simply does not.

a callback function may be used to provide feedback about the progress of the key generation. if cb is not NULL, it will be called as shown below. for information on the BN_GENCB structure and the BN_GENCB_call function discussed below, refer to BN_generate_prime(3) 📖

DSA_generate_parameters() is similar to DSA_generate_parameters_ex() but expects an old-style callback function; see BN_generate_prime(3) for information on the old-style callback. vintage callback, very retro of her 🙈

🦋 the callback tea, step by step 🦋

  • when a candidate for q is generated, BN_GENCB_call(cb, 0, m++) is called (m is 0 for the first candidate) ⭐
  • when a candidate for q has passed a test by trial division, BN_GENCB_call(cb, 1, -1) is called. while a candidate for q is tested by Miller-Rabin primality tests, BN_GENCB_call(cb, 1, i) is called in the outer loop (once for each witness that confirms that the candidate may be prime); i is the loop counter (starting at 0) 🔥
  • when a prime q has been found, BN_GENCB_call(cb, 2, 0) and BN_GENCB_call(cb, 3, 0) are called 👑
  • before a candidate for p (other than the first) is generated and tested, BN_GENCB_call(cb, 0, counter) is called 🌈
  • when a candidate for p has passed the test by trial division, BN_GENCB_call(cb, 1, -1) is called. while it is tested by the Miller-Rabin primality test, BN_GENCB_call(cb, 1, i) is called in the outer loop (once for each witness that confirms that the candidate may be prime). i is the loop counter (starting at 0) 💫
  • when p has been found, BN_GENCB_call(cb, 2, 1) is called ✅
  • when the generator has been found, BN_GENCB_call(cb, 3, 1) is called 🎉

🎀 RETURN VALUES 🎀

DSA_generate_parameters_ex() returns a 1 on success, or 0 otherwise. the error codes can be obtained by ERR_get_error(3) — go look them up, she'll tell you what went wrong 🕵️

DSA_generate_parameters() returns a pointer to the DSA structure or NULL if the parameter generation fails 💀

😭 BUGS 😭

seed lengths greater than 20 are not supported. that's it, that's the bug. twenty. twenty is the limit. don't test her.

🫶 SEE ALSO 🫶

👑 HISTORY 👑

  • DSA_generate_parameters_ex() was deprecated in OpenSSL 3.0 💔
  • DSA_generate_parameters() was deprecated in OpenSSL 0.9.8; use DSA_generate_parameters_ex() instead 🔁

Copyright 2000-2021 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>.

and that's the whole page, bestie!! this was OpenSSL 3.5.9, dated 2026-09-29, and you can find it filed under DSA_GENERATE_PARAMETERS(3ossl) 💖 go use EVP_PKEY_paramgen_init(3) and EVP_PKEY_keygen(3) instead though, fr fr. mwah 🫶✨

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