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DHPARAM(1)			    OpenSSL			    DHPARAM(1)

NAME
       openssl-dhparam,	dhparam	- DH parameter manipulation and	generation

SYNOPSIS
       openssl dhparam [-help] [-inform	DER|PEM] [-outform DER|PEM] [-in
       filename] [-out filename] [-dsaparam] [-check] [-noout] [-text] [-C]
       [-2] [-5] [-rand	file...]  [-writerand file] [-engine id] [numbits]

DESCRIPTION
       This command is used to manipulate DH parameter files.

OPTIONS
       -help
	   Print out a usage message.

       -inform DER|PEM
	   This	specifies the input format. The	DER option uses	an ASN1	DER
	   encoded form	compatible with	the PKCS#3 DHparameter structure. The
	   PEM form is the default format: it consists of the DER format
	   base64 encoded with additional header and footer lines.

       -outform	DER|PEM
	   This	specifies the output format, the options have the same meaning
	   and default as the -inform option.

       -in filename
	   This	specifies the input filename to	read parameters	from or
	   standard input if this option is not	specified.

       -out filename
	   This	specifies the output filename parameters to. Standard output
	   is used if this option is not present. The output filename should
	   not be the same as the input	filename.

       -dsaparam
	   If this option is used, DSA rather than DH parameters are read or
	   created; they are converted to DH format.  Otherwise, "strong"
	   primes (such	that (p-1)/2 is	also prime) will be used for DH
	   parameter generation.

	   DH parameter	generation with	the -dsaparam option is	much faster,
	   and the recommended exponent	length is shorter, which makes DH key
	   exchange more efficient.  Beware that with such DSA-style DH
	   parameters, a fresh DH key should be	created	for each use to	avoid
	   small-subgroup attacks that may be possible otherwise.

       -check
	   Performs numerous checks to see if the supplied parameters are
	   valid and displays a	warning	if not.

       -2, -5
	   The generator to use, either	2 or 5.	If present then	the input file
	   is ignored and parameters are generated instead. If not present but
	   numbits is present, parameters are generated	with the default
	   generator 2.

       -rand file...
	   A file or files containing random data used to seed the random
	   number generator.  Multiple files can be specified separated	by an
	   OS-dependent	character.  The	separator is ; for MS-Windows, , for
	   OpenVMS, and	: for all others.

       [-writerand file]
	   Writes random data to the specified file upon exit.	This can be
	   used	with a subsequent -rand	flag.

       numbits
	   This	option specifies that a	parameter set should be	generated of
	   size	numbits. It must be the	last option. If	this option is present
	   then	the input file is ignored and parameters are generated
	   instead. If this option is not present but a	generator (-2 or -5)
	   is present, parameters are generated	with a default length of 2048
	   bits.

       -noout
	   This	option inhibits	the output of the encoded version of the
	   parameters.

       -text
	   This	option prints out the DH parameters in human readable form.

       -C  This	option converts	the parameters into C code. The	parameters can
	   then	be loaded by calling the get_dhNNNN() function.

       -engine id
	   Specifying an engine	(by its	unique id string) will cause dhparam
	   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.

WARNINGS
       The program dhparam combines the	functionality of the programs dh and
       gendh in	previous versions of OpenSSL. The dh and gendh programs	are
       retained	for now	but may	have different purposes	in future versions of
       OpenSSL.

NOTES
       PEM format DH parameters	use the	header and footer lines:

	-----BEGIN DH PARAMETERS-----
	-----END DH PARAMETERS-----

       OpenSSL currently only supports the older PKCS#3	DH, not	the newer
       X9.42 DH.

       This program manipulates	DH parameters not keys.

BUGS
       There should be a way to	generate and manipulate	DH keys.

SEE ALSO
       dsaparam(1)

COPYRIGHT
       Copyright 2000-2017 The OpenSSL Project Authors.	All Rights Reserved.

       Licensed	under the OpenSSL license (the "License").  You	may not	use
       this file except	in compliance with the License.	 You can obtain	a copy
       in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.

1.1.1a				  2018-11-20			    DHPARAM(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | WARNINGS | NOTES | BUGS | SEE ALSO | COPYRIGHT

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