DSA_GENERATE_PARAMETERS(3SSL)

NAME
DSA_generate_parameters_ex, DSA_generate_parameters - generate DSA parameters

SYNOPSIS
 #include <openssl/dsa.h>

 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);

Deprecated:

 #if OPENSSL_API_COMPAT < 0x00908000L
 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);
 #endif

DESCRIPTION
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).

•   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.

DSA_generate_parameters() (deprecated) works in much the same way as for DSA_generate_parameters_ex, except that no dsa parameter is passed and instead a newly allocated DSA structure is returned. Additionally "old style" callbacks are used instead of the newer BN_GENCB based approach. Refer to BN_generate_prime(3) for further information.

RETURN VALUE
DSA_generate_parameters_ex() returns a 1 on success, or 0 otherwise.

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

The error codes can be obtained by ERR_get_error(3).

BUGS
Seed lengths > 20 are not supported.

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

COPYRIGHT
Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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>.