DSA_generate_parameters(3) LibreSSL DSA_generate_parameters(3)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:
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);
DESCRIPTIONDSA_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 to be generated; the DSS allows a
maximum of 1024 bits.
If seed is NULL or seed_len < 20, the primes will be generated at
random. Otherwise, the seed is used to generate them. If the given seed
does not yield a prime q, a new random seed is chosen and placed at
seed.
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 VALUEDSA_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 ALSOdsa(3), ERR_get_error(3), rand(3), DSA_free(3), BN_generate_prime(3)HISTORYDSA_generate_parameters() appeared in SSLeay 0.8. The cb_arg argument
was added in SSLeay 0.9.0. In versions up to OpenSSL 0.9.4,
callback(1, ...) was called in the inner loop of the Miller-Rabin test
whenever it reached the squaring step (the parameters to callback did
not reveal how many witnesses had been tested); since OpenSSL 0.9.5,
callback(1, ...) is called as in BN_is_prime(3), i.e. once for each
witness.
LibreSSL 2015-12-05 DSA_generate_parameters(3)
