.\"	$NetBSD: DSA_generate_parameters.3,v 1.13 2004/03/20 21:48:45 groo Exp $
.\"
.\" Automatically generated by Pod::Man version 1.15
.\" Sat Mar 20 16:40:57 2004
.\"
.\" Standard preamble:
.\" ======================================================================
.de Sh \" Subsection heading
.br
.if t .Sp
.ne 5
.PP
\fB\\$1\fR
.PP
..
.de Sp \" Vertical space (when we can't use .PP)
.if t .sp .5v
.if n .sp
..
.de Ip \" List item
.br
.ie \\n(.$>=3 .ne \\$3
.el .ne 3
.IP "\\$1" \\$2
..
.de Vb \" Begin verbatim text
.ft CW
.nf
.ne \\$1
..
.de Ve \" End verbatim text
.ft R

.fi
..
.\" Set up some character translations and predefined strings.  \*(-- will
.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
.\" double quote, and \*(R" will give a right double quote.  | will give a
.\" real vertical bar.  \*(C+ will give a nicer C++.  Capital omega is used
.\" to do unbreakable dashes and therefore won't be available.  \*(C` and
.\" \*(C' expand to `' in nroff, nothing in troff, for use with C<>
.tr \(*W-|\(bv\*(Tr
.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
.ie n \{\
.    ds -- \(*W-
.    ds PI pi
.    if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
.    if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\"  diablo 12 pitch
.    ds L" ""
.    ds R" ""
.    ds C` ""
.    ds C' ""
'br\}
.el\{\
.    ds -- \|\(em\|
.    ds PI \(*p
.    ds L" ``
.    ds R" ''
'br\}
.\"
.\" If the F register is turned on, we'll generate index entries on stderr
.\" for titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and
.\" index entries marked with X<> in POD.  Of course, you'll have to process
.\" the output yourself in some meaningful fashion.
.if \nF \{\
.    de IX
.    tm Index:\\$1\t\\n%\t"\\$2"
..
.    nr % 0
.    rr F
.\}
.\"
.\" For nroff, turn off justification.  Always turn off hyphenation; it
.\" makes way too many mistakes in technical documents.
.hy 0
.if n .na
.\"
.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
.\" Fear.  Run.  Save yourself.  No user-serviceable parts.
.bd B 3
.    \" fudge factors for nroff and troff
.if n \{\
.    ds #H 0
.    ds #V .8m
.    ds #F .3m
.    ds #[ \f1
.    ds #] \fP
.\}
.if t \{\
.    ds #H ((1u-(\\\\n(.fu%2u))*.13m)
.    ds #V .6m
.    ds #F 0
.    ds #[ \&
.    ds #] \&
.\}
.    \" simple accents for nroff and troff
.if n \{\
.    ds ' \&
.    ds ` \&
.    ds ^ \&
.    ds , \&
.    ds ~ ~
.    ds /
.\}
.if t \{\
.    ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
.    ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
.    ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
.    ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
.    ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
.    ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
.\}
.    \" troff and (daisy-wheel) nroff accents
.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
.ds 8 \h'\*(#H'\(*b\h'-\*(#H'
.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
.ds ae a\h'-(\w'a'u*4/10)'e
.ds Ae A\h'-(\w'A'u*4/10)'E
.    \" corrections for vroff
.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
.    \" for low resolution devices (crt and lpr)
.if \n(.H>23 .if \n(.V>19 \
\{\
.    ds : e
.    ds 8 ss
.    ds o a
.    ds d- d\h'-1'\(ga
.    ds D- D\h'-1'\(hy
.    ds th \o'bp'
.    ds Th \o'LP'
.    ds ae ae
.    ds Ae AE
.\}
.rm #[ #] #H #V #F C
.\" ======================================================================
.\"
.IX Title "DSA_generate_parameters 3"
.TH DSA_generate_parameters 3 "0.9.7d" "2003-09-24" "OpenSSL"
.UC
.SH "NAME"
DSA_generate_parameters \- generate \s-1DSA\s0 parameters
.SH "LIBRARY"
libcrypto, -lcrypto
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.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"
.IX Header "DESCRIPTION"
\&\fIDSA_generate_parameters()\fR generates primes p and q and a generator g
for use in the \s-1DSA\s0.
.PP
\&\fBbits\fR is the length of the prime to be generated; the \s-1DSS\s0 allows a
maximum of 1024 bits.
.PP
If \fBseed\fR is \fB\s-1NULL\s0\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 \fB\s-1NULL\s0\fR.
.PP
A callback function may be used to provide feedback about the progress
of the key generation. If \fBcallback\fR is not \fB\s-1NULL\s0\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"
.IX Header "RETURN VALUE"
\&\fIDSA_generate_parameters()\fR returns a pointer to the \s-1DSA\s0 structure, or
\&\fB\s-1NULL\s0\fR if the parameter generation fails. The error codes can be
obtained by ERR_get_error(3).
.SH "BUGS"
.IX Header "BUGS"
Seed lengths > 20 are not supported.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
openssl_dsa(3), ERR_get_error(3), openssl_rand(3),
DSA_free(3)
.SH "HISTORY"
.IX Header "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