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OPENSSL-DHPARAM(1SSL) OpenSSL OPENSSL-DHPARAM(1SSL)
NAME
openssl-dhparam - DH parameter manipulation and generation
SYNOPSIS
openssl dhparam [-help] [-inform DER|PEM] [-outform DER|PEM] [-in filename] [-out
filename] [-dsaparam] [-check] [-noout] [-text] [-2] [-3] [-5] [-engine id] [-rand files]
[-writerand file] [-provider name] [-provider-path path] [-propquery propq] [numbits]
DESCRIPTION
This command is used to manipulate DH parameter files.
See "EXAMPLES" in openssl-genpkey(1) for examples on how to generate a key using a named
safe prime group without generating intermediate parameters.
OPTIONS
-help
Print out a usage message.
-inform DER|PEM, -outform DER|PEM
The input format and output format; the default is PEM. The object is compatible with
the PKCS#3 DHparameter structure. See openssl-format-options(1) for details.
-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, -3, -5
The generator to use, either 2, 3 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.
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,
-3 or -5) is present, parameters are generated with a default length of 2048 bits.
The minimim length is 512 bits. The maximum length is 10000 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.
-engine id
See "Engine Options" in openssl(1). This option is deprecated.
-rand files, -writerand file
See "Random State Options" in openssl(1) for details.
-provider name
-provider-path path
-propquery propq
See "Provider Options" in openssl(1), provider(7), and property(7).
NOTES
This command replaces the dh and gendh commands of previous releases.
SEE ALSO
openssl(1), openssl-pkeyparam(1), openssl-dsaparam(1), openssl-genpkey(1).
HISTORY
The -engine option was deprecated in OpenSSL 3.0.
The -C option was removed in OpenSSL 3.0.
COPYRIGHT
Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (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>.
3.0.2 2024-08-20 OPENSSL-DHPARAM(1SSL)
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Under GNU General Public License
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