5 DSA_generate_parameters - generate DSA parameters
9 #include <openssl/dsa.h>
11 DSA *DSA_generate_parameters(int bits, unsigned char *seed,
12 int seed_len, int *counter_ret, unsigned long *h_ret,
13 void (*callback)(int, int, void *), void *cb_arg);
17 DSA_generate_parameters() generates primes p and q and a generator g
20 B<bits> is the length of the prime p to be generated.
21 For lengths under 2048 bits, the length of q is 160 bits; for lengths
22 at least 2048, it is set to 256 bits.
24 If B<seed> is NULL, the primes will be generated at random.
25 If B<seed_len> is less than the length of q, an error is returned.
27 DSA_generate_parameters() places the iteration count in
28 *B<counter_ret> and a counter used for finding a generator in
29 *B<h_ret>, unless these are B<NULL>.
31 A callback function may be used to provide feedback about the progress
32 of the key generation. If B<callback> is not B<NULL>, it will be
39 When a candidate for q is generated, B<callback(0, m++, cb_arg)> is called
40 (m is 0 for the first candidate).
44 When a candidate for q has passed a test by trial division,
45 B<callback(1, -1, cb_arg)> is called.
46 While a candidate for q is tested by Miller-Rabin primality tests,
47 B<callback(1, i, cb_arg)> is called in the outer loop
48 (once for each witness that confirms that the candidate may be prime);
49 i is the loop counter (starting at 0).
53 When a prime q has been found, B<callback(2, 0, cb_arg)> and
54 B<callback(3, 0, cb_arg)> are called.
58 Before a candidate for p (other than the first) is generated and tested,
59 B<callback(0, counter, cb_arg)> is called.
63 When a candidate for p has passed the test by trial division,
64 B<callback(1, -1, cb_arg)> is called.
65 While it is tested by the Miller-Rabin primality test,
66 B<callback(1, i, cb_arg)> is called in the outer loop
67 (once for each witness that confirms that the candidate may be prime).
68 i is the loop counter (starting at 0).
72 When p has been found, B<callback(2, 1, cb_arg)> is called.
76 When the generator has been found, B<callback(3, 1, cb_arg)> is called.
82 DSA_generate_parameters() returns a pointer to the DSA structure, or
83 B<NULL> if the parameter generation fails. The error codes can be
84 obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
88 Seed lengths E<gt> 20 are not supported.
92 L<dsa(3)|dsa(3)>, L<ERR_get_error(3)|ERR_get_error(3)>, L<rand(3)|rand(3)>,
93 L<DSA_free(3)|DSA_free(3)>
97 DSA_generate_parameters() appeared in SSLeay 0.8. The B<cb_arg>
98 argument was added in SSLeay 0.9.0.
99 In versions up to OpenSSL 0.9.4, B<callback(1, ...)> was called
100 in the inner loop of the Miller-Rabin test whenever it reached the
101 squaring step (the parameters to B<callback> did not reveal how many
102 witnesses had been tested); since OpenSSL 0.9.5, B<callback(1, ...)>
103 is called as in BN_is_prime(3), i.e. once for each witness.