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.\" ========================================================================
.\"
.IX Title "DSA_GENERATE_PARAMETERS 3"
.TH DSA_GENERATE_PARAMETERS 3 "2024-10-09" "1.1.1k" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
DSA_generate_parameters_ex, DSA_generate_parameters \- generate DSA parameters
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #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);
.Ve
.PP
Deprecated:
.PP
.Vb 5
\& #if OPENSSL_API_COMPAT < 0x00908000L
\& 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);
\& #endif
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBDSA_generate_parameters_ex()\fR generates primes p and q and a generator g
for use in the \s-1DSA\s0 and stores the result in \fBdsa\fR.
.PP
\&\fBbits\fR is the length of the prime p to be generated.
For lengths under 2048 bits, the length of q is 160 bits; for lengths
greater than or equal to 2048 bits, the length of q is set to 256 bits.
.PP
If \fBseed\fR is \s-1NULL,\s0 or it does not generate primes, the primes will be
generated at random.
If \fBseed_len\fR is less than the length of q, an error is returned
if old \s-1DSA\s0 parameter generation method is used as a backend.
.PP
\&\fBDSA_generate_parameters_ex()\fR places the iteration count in
*\fBcounter_ret\fR and a counter used for finding a generator in
*\fBh_ret\fR, unless these are \fB\s-1NULL\s0\fR.
.PP
A callback function may be used to provide feedback about the progress
of the key generation. If \fBcb\fR is not \fB\s-1NULL\s0\fR, it will be
called as shown below. For information on the \s-1BN_GENCB\s0 structure and the
BN_GENCB_call function discussed below, refer to
\&\fBBN_generate_prime\fR\|(3).
.PP
\&\fBDSA_generate_prime()\fR is similar to \fBDSA_generate_prime_ex()\fR but
expects an old-style callback function; see
\&\fBBN_generate_prime\fR\|(3) for information on the old-style callback.
.IP "\(bu" 2
When a candidate for q is generated, \fBBN_GENCB_call(cb, 0, m++)\fR is called
(m is 0 for the first candidate).
.IP "\(bu" 2
When a candidate for q has passed a test by trial division,
\&\fBBN_GENCB_call(cb, 1, \-1)\fR is called.
While a candidate for q is tested by Miller-Rabin primality tests,
\&\fBBN_GENCB_call(cb, 1, i)\fR 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).
.IP "\(bu" 2
When a prime q has been found, \fBBN_GENCB_call(cb, 2, 0)\fR and
\&\fBBN_GENCB_call(cb, 3, 0)\fR are called.
.IP "\(bu" 2
Before a candidate for p (other than the first) is generated and tested,
\&\fBBN_GENCB_call(cb, 0, counter)\fR is called.
.IP "\(bu" 2
When a candidate for p has passed the test by trial division,
\&\fBBN_GENCB_call(cb, 1, \-1)\fR is called.
While it is tested by the Miller-Rabin primality test,
\&\fBBN_GENCB_call(cb, 1, i)\fR 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).
.IP "\(bu" 2
When p has been found, \fBBN_GENCB_call(cb, 2, 1)\fR is called.
.IP "\(bu" 2
When the generator has been found, \fBBN_GENCB_call(cb, 3, 1)\fR is called.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBDSA_generate_parameters_ex()\fR returns a 1 on success, or 0 otherwise.
The error codes can be obtained by \fBERR_get_error\fR\|(3).
.PP
\&\fBDSA_generate_parameters()\fR returns a pointer to the \s-1DSA\s0 structure or
\&\fB\s-1NULL\s0\fR if the parameter generation fails.
.SH "BUGS"
.IX Header "BUGS"
Seed lengths greater than 20 are not supported.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBDSA_new\fR\|(3), \fBERR_get_error\fR\|(3), \fBRAND_bytes\fR\|(3),
\&\fBDSA_free\fR\|(3), \fBBN_generate_prime\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
\&\fBDSA_generate_parameters()\fR was deprecated in OpenSSL 0.9.8; use
\&\fBDSA_generate_parameters_ex()\fR instead.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2018 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.
