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,
14                                BN_GENCB *cb);
15
16Deprecated:
17
18 #if OPENSSL_API_COMPAT < 0x00908000L
19 DSA *DSA_generate_parameters(int bits, unsigned char *seed, int seed_len,
20                              int *counter_ret, unsigned long *h_ret,
21                              void (*callback)(int, int, void *), void *cb_arg);
22 #endif
23
24=head1 DESCRIPTION
25
26DSA_generate_parameters_ex() generates primes p and q and a generator g
27for use in the DSA and stores the result in B<dsa>.
28
29B<bits> is the length of the prime p to be generated.
30For lengths under 2048 bits, the length of q is 160 bits; for lengths
31greater than or equal to 2048 bits, the length of q is set to 256 bits.
32
33If B<seed> is NULL, the primes will be generated at random.
34If B<seed_len> is less than the length of q, an error is returned.
35
36DSA_generate_parameters_ex() places the iteration count in
37*B<counter_ret> and a counter used for finding a generator in
38*B<h_ret>, unless these are B<NULL>.
39
40A callback function may be used to provide feedback about the progress
41of the key generation. If B<cb> is not B<NULL>, it will be
42called as shown below. For information on the BN_GENCB structure and the
43BN_GENCB_call function discussed below, refer to
44L<BN_generate_prime(3)>.
45
46DSA_generate_prime() is similar to DSA_generate_prime_ex() but
47expects an old-style callback function; see
48L<BN_generate_prime(3)> for information on the old-style callback.
49
50=over 2
51
52=item *
53
54When a candidate for q is generated, B<BN_GENCB_call(cb, 0, m++)> is called
55(m is 0 for the first candidate).
56
57=item *
58
59When a candidate for q has passed a test by trial division,
60B<BN_GENCB_call(cb, 1, -1)> is called.
61While a candidate for q is tested by Miller-Rabin primality tests,
62B<BN_GENCB_call(cb, 1, i)> is called in the outer loop
63(once for each witness that confirms that the candidate may be prime);
64i is the loop counter (starting at 0).
65
66=item *
67
68When a prime q has been found, B<BN_GENCB_call(cb, 2, 0)> and
69B<BN_GENCB_call(cb, 3, 0)> are called.
70
71=item *
72
73Before a candidate for p (other than the first) is generated and tested,
74B<BN_GENCB_call(cb, 0, counter)> is called.
75
76=item *
77
78When a candidate for p has passed the test by trial division,
79B<BN_GENCB_call(cb, 1, -1)> is called.
80While it is tested by the Miller-Rabin primality test,
81B<BN_GENCB_call(cb, 1, i)> is called in the outer loop
82(once for each witness that confirms that the candidate may be prime).
83i is the loop counter (starting at 0).
84
85=item *
86
87When p has been found, B<BN_GENCB_call(cb, 2, 1)> is called.
88
89=item *
90
91When the generator has been found, B<BN_GENCB_call(cb, 3, 1)> is called.
92
93=back
94
95=head1 RETURN VALUES
96
97DSA_generate_parameters_ex() returns a 1 on success, or 0 otherwise.
98The error codes can be obtained by L<ERR_get_error(3)>.
99
100DSA_generate_parameters() returns a pointer to the DSA structure or
101B<NULL> if the parameter generation fails.
102
103=head1 BUGS
104
105Seed lengths greater than 20 are not supported.
106
107=head1 SEE ALSO
108
109L<DSA_new(3)>, L<ERR_get_error(3)>, L<RAND_bytes(3)>,
110L<DSA_free(3)>, L<BN_generate_prime(3)>
111
112=head1 HISTORY
113
114DSA_generate_parameters() was deprecated in OpenSSL 0.9.8; use
115DSA_generate_parameters_ex() instead.
116
117=head1 COPYRIGHT
118
119Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
120
121Licensed under the OpenSSL license (the "License").  You may not use
122this file except in compliance with the License.  You can obtain a copy
123in the file LICENSE in the source distribution or at
124L<https://www.openssl.org/source/license.html>.
125
126=cut
127