DSA_GENERATE_PARAMETERS(3SSL)

📦
version 4.0.3 · 13 versions
, in ubuntu stonking

💖 DSA_GENERATE_PARAMETERS(3SSL) 💖

okay bestie, pull up a chair, we're reading an OpenSSL manpage together and honestly? it's a whole journey. this one lives in the OpenSSL section 3SSL of the manual, and it's literally called DSA_generate_parameters_ex, DSA_generate_parameters — the girls who generate DSA parameters. and no, they are not the main characters anymore, but we still love them and we still gotta know them. 🫶

✨ NAME ✨

DSA_generate_parameters_ex, DSA_generate_parameters — generate DSA parameters. that's it, that's the whole job. 💅

🦋 SYNOPSIS 🦋

first, the entrance:

#include <openssl/dsa.h>

now listen, these next ones have been deprecated since OpenSSL 3.0, and you can hide them entirely by defining OPENSSL_API_COMPAT with a suitable version value — see openssl_user_macros(7) for the tea:

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);

and this one? deprecated since OpenSSL 0.9.8, like, ancient history, grandmother era. it can also 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 🌸

okay so, every single function on this page is deprecated. girly pop, that's not a vibe check you want to fail. 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. ✨

but if we're being nosy about what these do: DSA_generate_parameters_ex() generates primes p and q and a generator g for use in the DSA, and stores the result in dsa.

bits is the length of the prime p to be generated. and here's the little rule, no cap:

  • 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 🎲. if seed_len is less than the length of q, an error is returned. periodt.

DSA_generate_parameters_ex() places the iteration count in *counter_ret and a counter used for finding a generator in *h_ret, unless these are NULL.

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.

and now, the callback receipts, in order, iconically:

  • 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.

like, the callback really said "I'll narrate the whole thing, you're welcome." 💅

💀 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). so if you got a 0, go ask ERR_get_error(3) what happened, she always knows.

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 the whole bug section. short, sweet, and mildly devastating. 😭

🎀 SEE ALSO 🎀

go read your sisters, bestie:

👑 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.

the way they've been deprecated for years and are still here… lowkey iconic for surviving this long, highkey time to move on. 🧚

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>.

tiny reminder bestie: this page is from OpenSSL version 4.0.3, dated 2026-09-29, and it beloveds to the DSA_GENERATE_PARAMETERS(3SSL) manual. 💖 thanks for reading the whole thing with me, you ate that fr fr. mwah 🫶✨
📦 where this page comes from