NAME¶
DSA_generate_parameters - generate DSA parameters
SYNOPSIS¶
#include <openssl/dsa.h>
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¶
DSA_generate_parameters() generates primes p and q and a generator g for
use in the 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.
DSA_generate_parameters() 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
callback is not
NULL, it will be called as
follows:
- •
- When a candidate for q is generated, callback(0, m++, cb_arg) is
called (m is 0 for the first candidate).
- •
- When a candidate for q has passed a test by trial division, callback(1,
-1, cb_arg) is called. While a candidate for q is tested by
Miller-Rabin primality tests, callback(1, i, cb_arg) 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, callback(2, 0, cb_arg) and
callback(3, 0, cb_arg) are called.
- •
- Before a candidate for p (other than the first) is generated and tested,
callback(0, counter, cb_arg) is called.
- •
- When a candidate for p has passed the test by trial division,
callback(1, -1, cb_arg) is called. While it is tested by the
Miller-Rabin primality test, callback(1, i, cb_arg) 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, callback(2, 1, cb_arg) is called.
- •
- When the generator has been found, callback(3, 1, cb_arg) is
called.
RETURN VALUE¶
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(3),
ERR_get_error(3),
rand(3),
DSA_free(3)
HISTORY¶
DSA_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.