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);
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 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_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(3),
ERR_get_error(3),
rand(3),
DSA_free(3),
BN_generate_prime(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.