NetBSD/lib/libcrypto/man/DSA_generate_parameters.3

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.TH DSA_generate_parameters 3 "0.9.5a" "22/Jul/2000" "OpenSSL"
.UC
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.rm #[ #] #H #V #F C
.SH "NAME"
DSA_generate_parameters \- generate DSA parameters
.SH "LIBRARY"
libcrypto, -lcrypto
.SH "SYNOPSIS"
.PP
.Vb 1
\& #include <openssl/dsa.h>
.Ve
.Vb 3
\& 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);
.Ve
.SH "DESCRIPTION"
\fIDSA_generate_parameters()\fR generates primes p and q and a generator g
for use in the DSA.
.PP
\fBbits\fR is the length of the prime to be generated; the DSS allows a
maximum of 1024 bits.
.PP
If \fBseed\fR is \fBNULL\fR or \fBseed_len\fR < 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 \fBseed\fR.
.PP
\fIDSA_generate_parameters()\fR places the iteration count in
*\fBcounter_ret\fR and a counter used for finding a generator in
*\fBh_ret\fR, unless these are \fBNULL\fR.
.PP
A callback function may be used to provide feedback about the progress
of the key generation. If \fBcallback\fR is not \fBNULL\fR, it will be
called as follows:
.Ip "\(bu" 4
When a candidate for q is generated, \fBcallback(0, m++, cb_arg)\fR is called
(m is 0 for the first candidate).
.Ip "\(bu" 4
When a candidate for q has passed a test by trial division,
\fBcallback(1, \-1, cb_arg)\fR is called.
While a candidate for q is tested by Miller-Rabin primality tests,
\fBcallback(1, i, cb_arg)\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" 4
When a prime q has been found, \fBcallback(2, 0, cb_arg)\fR and
\fBcallback(3, 0, cb_arg)\fR are called.
.Ip "\(bu" 4
Before a candidate for p (other than the first) is generated and tested,
\fBcallback(0, counter, cb_arg)\fR is called.
.Ip "\(bu" 4
When a candidate for p has passed the test by trial division,
\fBcallback(1, \-1, cb_arg)\fR is called.
While it is tested by the Miller-Rabin primality test,
\fBcallback(1, i, cb_arg)\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" 4
When p has been found, \fBcallback(2, 1, cb_arg)\fR is called.
.Ip "\(bu" 4
When the generator has been found, \fBcallback(3, 1, cb_arg)\fR is called.
.SH "RETURN VALUE"
\fIDSA_generate_parameters()\fR returns a pointer to the DSA structure, or
\fBNULL\fR if the parameter generation fails. The error codes can be
obtained by the \fIERR_get_error(3)|ERR_get_error(3)\fR manpage.
.SH "BUGS"
Seed lengths > 20 are not supported.
.SH "SEE ALSO"
the \fIdsa(3)|dsa(3)\fR manpage, the \fIerr(3)|err(3)\fR manpage, the \fIrand(3)|rand(3)\fR manpage,
the \fIDSA_free(3)|DSA_free(3)\fR manpage
.SH "HISTORY"
\fIDSA_generate_parameters()\fR appeared in SSLeay 0.8. The \fBcb_arg\fR
argument was added in SSLeay 0.9.0.
In versions up to OpenSSL 0.9.4, \fBcallback(1, ...)\fR was called
in the inner loop of the Miller-Rabin test whenever it reached the
squaring step (the parameters to \fBcallback\fR did not reveal how many
witnesses had been tested); since OpenSSL 0.9.5, \fBcallback(1, ...)\fR
is called as in \fIBN_is_prime\fR\|(3), i.e. once for each witness.
=cut
.rn }` ''
.IX Title "DSA_generate_parameters 3"
.IX Name "DSA_generate_parameters - generate DSA parameters"
.IX Header "NAME"
.IX Header "SYNOPSIS"
.IX Header "DESCRIPTION"
.IX Item "\(bu"
.IX Item "\(bu"
.IX Item "\(bu"
.IX Item "\(bu"
.IX Item "\(bu"
.IX Item "\(bu"
.IX Item "\(bu"
.IX Header "RETURN VALUE"
.IX Header "BUGS"
.IX Header "SEE ALSO"
.IX Header "HISTORY"