1=pod 2 3=head1 NAME 4 5DSA_generate_parameters_ex, DSA_generate_parameters - generate DSA parameters 6 7=head1 SYNOPSIS 8 9 #include <openssl/dsa.h> 10 11 int DSA_generate_parameters_ex(DSA *dsa, int bits, 12 const unsigned char *seed,int seed_len, 13 int *counter_ret, unsigned long *h_ret, BN_GENCB *cb); 14 15Deprecated: 16 17 DSA *DSA_generate_parameters(int bits, unsigned char *seed, 18 int seed_len, int *counter_ret, unsigned long *h_ret, 19 void (*callback)(int, int, void *), void *cb_arg); 20 21=head1 DESCRIPTION 22 23DSA_generate_parameters_ex() generates primes p and q and a generator g 24for use in the DSA and stores the result in B<dsa>. 25 26B<bits> is the length of the prime to be generated; the DSS allows a 27maximum of 1024 bits. 28 29If B<seed> is B<NULL> or B<seed_len> E<lt> 20, the primes will be 30generated at random. Otherwise, the seed is used to generate 31them. If the given seed does not yield a prime q, a new random 32seed is chosen. 33 34DSA_generate_parameters_ex() places the iteration count in 35*B<counter_ret> and a counter used for finding a generator in 36*B<h_ret>, unless these are B<NULL>. 37 38A callback function may be used to provide feedback about the progress 39of the key generation. If B<cb> is not B<NULL>, it will be 40called as shown below. For information on the BN_GENCB structure and the 41BN_GENCB_call function discussed below, refer to 42L<BN_generate_prime(3)|BN_generate_prime(3)>. 43 44=over 4 45 46=item * 47 48When a candidate for q is generated, B<BN_GENCB_call(cb, 0, m++)> is called 49(m is 0 for the first candidate). 50 51=item * 52 53When a candidate for q has passed a test by trial division, 54B<BN_GENCB_call(cb, 1, -1)> is called. 55While a candidate for q is tested by Miller-Rabin primality tests, 56B<BN_GENCB_call(cb, 1, i)> is called in the outer loop 57(once for each witness that confirms that the candidate may be prime); 58i is the loop counter (starting at 0). 59 60=item * 61 62When a prime q has been found, B<BN_GENCB_call(cb, 2, 0)> and 63B<BN_GENCB_call(cb, 3, 0)> are called. 64 65=item * 66 67Before a candidate for p (other than the first) is generated and tested, 68B<BN_GENCB_call(cb, 0, counter)> is called. 69 70=item * 71 72When a candidate for p has passed the test by trial division, 73B<BN_GENCB_call(cb, 1, -1)> is called. 74While it is tested by the Miller-Rabin primality test, 75B<BN_GENCB_call(cb, 1, i)> is called in the outer loop 76(once for each witness that confirms that the candidate may be prime). 77i is the loop counter (starting at 0). 78 79=item * 80 81When p has been found, B<BN_GENCB_call(cb, 2, 1)> is called. 82 83=item * 84 85When the generator has been found, B<BN_GENCB_call(cb, 3, 1)> is called. 86 87=back 88 89DSA_generate_parameters() (deprecated) works in much the same way as for DSA_generate_parameters_ex, except that no B<dsa> parameter is passed and 90instead a newly allocated B<DSA> structure is returned. Additionally "old 91style" callbacks are used instead of the newer BN_GENCB based approach. 92Refer to L<BN_generate_prime(3)|BN_generate_prime(3)> for further information. 93 94=head1 RETURN VALUE 95 96DSA_generate_parameters_ex() returns a 1 on success, or 0 otherwise. 97 98DSA_generate_parameters() returns a pointer to the DSA structure, or 99B<NULL> if the parameter generation fails. 100 101The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>. 102 103=head1 BUGS 104 105Seed lengths E<gt> 20 are not supported. 106 107=head1 SEE ALSO 108 109L<dsa(3)|dsa(3)>, L<ERR_get_error(3)|ERR_get_error(3)>, L<rand(3)|rand(3)>, 110L<DSA_free(3)|DSA_free(3)>, L<BN_generate_prime(3)|BN_generate_prime(3)> 111 112=head1 HISTORY 113 114DSA_generate_parameters() appeared in SSLeay 0.8. The B<cb_arg> 115argument was added in SSLeay 0.9.0. 116In versions up to OpenSSL 0.9.4, B<callback(1, ...)> was called 117in the inner loop of the Miller-Rabin test whenever it reached the 118squaring step (the parameters to B<callback> did not reveal how many 119witnesses had been tested); since OpenSSL 0.9.5, B<callback(1, ...)> 120is called as in BN_is_prime(3), i.e. once for each witness. 121=cut 122