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DHPARAM(1)			    OpenSSL			    DHPARAM(1)

       dhparam - DH parameter manipulation and generation

       openssl dhparam [-inform	DER|PEM] [-outform DER|PEM] [-in filename]
       [-out filename] [-dsaparam] [-noout] [-text] [-C] [-2] [-5] [-rand
       file(s)]	[-engine id] [numbits]

       This command is used to manipulate DH parameter files.

       -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
	   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.

	   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.

       -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

       -rand file(s)
	   a file or files containing random data used to seed the random
	   number generator, or	an EGD socket (see RAND_egd(3)).  Multiple
	   files can be	specified separated by a OS-dependent character.  The
	   separator is	; for MS-Windows, , for	OpenVMS, and : for all others.

	   this	option specifies that a	parameter set should be	generated of
	   size	numbits. 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.

	   this	option inhibits	the output of the encoded version of the

	   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_dhnumbits() function.

       -engine id
	   specifying an engine	(by it's unique	id string) will	cause req 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.

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

       PEM format DH parameters	use the	header and footer lines:


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

       This program manipulates	DH parameters not keys.

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


       The dhparam command was added in	OpenSSL	0.9.5.	The -dsaparam option
       was added in OpenSSL 0.9.6.

0.9.8y				  2013-02-05			    DHPARAM(1)


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