## table of contents

DSA_GENERATE_PARAMETERS(3SSL) | OpenSSL | DSA_GENERATE_PARAMETERS(3SSL) |

# NAME¶

DSA_generate_parameters_ex, DSA_generate_parameters - generate DSA parameters

# SYNOPSIS¶

#include <openssl/dsa.h>

The following functions have been deprecated since OpenSSL 3.0,
and can be hidden entirely by defining **OPENSSL_API_COMPAT** with a
suitable version value, see openssl_user_macros(7):

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 following functions have been deprecated since OpenSSL 0.9.8,
and 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¶

All of the functions described on this page are deprecated. Applications should instead use EVP_PKEY_paramgen_init(3) and EVP_PKEY_keygen(3) as described in EVP_PKEY-DSA(7).

**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. 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.

**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_prime()** is similar to
**DSA_generate_prime_ex()** but expects an old-style callback function;
see BN_generate_prime(3) for information on the old-style
callback.

- 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).

**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.

# SEE ALSO¶

DSA_new(3), ERR_get_error(3), RAND_bytes(3), DSA_free(3), BN_generate_prime(3)

# 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¶

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>.

2022-08-14 | 3.0.5 |