NetBSD-5.0.2/lib/libcrypto/man/openssl_dhparam.1
.\" $NetBSD: openssl_dhparam.1,v 1.18 2008/05/09 22:02:44 christos Exp $
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.\" ========================================================================
.\"
.IX Title "DHPARAM 1"
.TH DHPARAM 1 "2003-07-24" "0.9.9-dev" "OpenSSL"
.SH "NAME"
dhparam \- DH parameter manipulation and generation
.SH "LIBRARY"
libcrypto, -lcrypto
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
\&\fBopenssl dhparam\fR
[\fB\-inform DER|PEM\fR]
[\fB\-outform DER|PEM\fR]
[\fB\-in\fR \fIfilename\fR]
[\fB\-out\fR \fIfilename\fR]
[\fB\-dsaparam\fR]
[\fB\-noout\fR]
[\fB\-text\fR]
[\fB\-C\fR]
[\fB\-2\fR]
[\fB\-5\fR]
[\fB\-rand\fR \fIfile(s)\fR]
[\fB\-engine id\fR]
[\fInumbits\fR]
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This command is used to manipulate \s-1DH\s0 parameter files.
.SH "OPTIONS"
.IX Header "OPTIONS"
.IP "\fB\-inform DER|PEM\fR" 4
.IX Item "-inform DER|PEM"
This specifies the input format. The \fB\s-1DER\s0\fR option uses an \s-1ASN1\s0 \s-1DER\s0 encoded
form compatible with the PKCS#3 DHparameter structure. The \s-1PEM\s0 form is the
default format: it consists of the \fB\s-1DER\s0\fR format base64 encoded with
additional header and footer lines.
.IP "\fB\-outform DER|PEM\fR" 4
.IX Item "-outform DER|PEM"
This specifies the output format, the options have the same meaning as the
\&\fB\-inform\fR option.
.IP "\fB\-in\fR \fIfilename\fR" 4
.IX Item "-in filename"
This specifies the input filename to read parameters from or standard input if
this option is not specified.
.IP "\fB\-out\fR \fIfilename\fR" 4
.IX Item "-out filename"
This specifies the output filename parameters to. Standard output is used
if this option is not present. The output filename should \fBnot\fR be the same
as the input filename.
.IP "\fB\-dsaparam\fR" 4
.IX Item "-dsaparam"
If this option is used, \s-1DSA\s0 rather than \s-1DH\s0 parameters are read or created;
they are converted to \s-1DH\s0 format. Otherwise, \*(L"strong\*(R" primes (such
that (p\-1)/2 is also prime) will be used for \s-1DH\s0 parameter generation.
.Sp
\&\s-1DH\s0 parameter generation with the \fB\-dsaparam\fR option is much faster,
and the recommended exponent length is shorter, which makes \s-1DH\s0 key
exchange more efficient. Beware that with such DSA-style \s-1DH\s0
parameters, a fresh \s-1DH\s0 key should be created for each use to
avoid small-subgroup attacks that may be possible otherwise.
.IP "\fB\-2\fR, \fB\-5\fR" 4
.IX Item "-2, -5"
The generator to use, either 2 or 5. 2 is the default. If present then the
input file is ignored and parameters are generated instead.
.IP "\fB\-rand\fR \fIfile(s)\fR" 4
.IX Item "-rand file(s)"
a file or files containing random data used to seed the random number
generator, or an \s-1EGD\s0 socket (see \fIRAND_egd\fR\|(3)).
Multiple files can be specified separated by a OS-dependent character.
The separator is \fB;\fR for MS\-Windows, \fB,\fR for OpenVMS, and \fB:\fR for
all others.
.IP "\fInumbits\fR" 4
.IX Item "numbits"
this option specifies that a parameter set should be generated of size
\&\fInumbits\fR. It must be the last option. If not present then a value of 512
is used. If this option is present then the input file is ignored and
parameters are generated instead.
.IP "\fB\-noout\fR" 4
.IX Item "-noout"
this option inhibits the output of the encoded version of the parameters.
.IP "\fB\-text\fR" 4
.IX Item "-text"
this option prints out the \s-1DH\s0 parameters in human readable form.
.IP "\fB\-C\fR" 4
.IX Item "-C"
this option converts the parameters into C code. The parameters can then
be loaded by calling the \fBget_dh\fR\fInumbits\fR\fB()\fR function.
.IP "\fB\-engine id\fR" 4
.IX Item "-engine id"
specifying an engine (by it's unique \fBid\fR string) will cause \fBreq\fR
to attempt to obtain a functional reference to the specified engine,
thus initialising it if needed. The engine will then be set as the default
for all available algorithms.
.SH "WARNINGS"
.IX Header "WARNINGS"
The program \fBdhparam\fR combines the functionality of the programs \fBdh\fR and
\&\fBgendh\fR in previous versions of OpenSSL and SSLeay. The \fBdh\fR and \fBgendh\fR
programs are retained for now but may have different purposes in future
versions of OpenSSL.
.SH "NOTES"
.IX Header "NOTES"
\&\s-1PEM\s0 format \s-1DH\s0 parameters use the header and footer lines:
.PP
.Vb 2
\& -----BEGIN DH PARAMETERS-----
\& -----END DH PARAMETERS-----
.Ve
.PP
OpenSSL currently only supports the older PKCS#3 \s-1DH\s0, not the newer X9.42
\&\s-1DH\s0.
.PP
This program manipulates \s-1DH\s0 parameters not keys.
.SH "BUGS"
.IX Header "BUGS"
There should be a way to generate and manipulate \s-1DH\s0 keys.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fIopenssl_dsaparam\fR\|(1)
.SH "HISTORY"
.IX Header "HISTORY"
The \fBdhparam\fR command was added in OpenSSL 0.9.5.
The \fB\-dsaparam\fR option was added in OpenSSL 0.9.6.