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 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, refer to
BN_GENCB_call(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) andBN_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 VALUES
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).
SEE ALSO
HISTORY
DSA_generate_parameters() first appeared
in SSLeay 0.8.0 and had its cb_arg argument added in
SSLeay 0.9.0. It has been available since OpenBSD
2.4.
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_ex(3), i.e. once for each witness.
DSA_generate_parameters_ex() first
appeared in OpenSSL 0.9.8 and has been available since
OpenBSD 4.5.
BUGS
Seed lengths > 20 are not supported.