openssl-dhparam - DH parameter manipulation and generation
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]
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.
- -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 minimum 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).
This command replaces the dh and gendh commands of
previous releases.
The -engine option was deprecated in OpenSSL 3.0.
The -C option was removed in OpenSSL 3.0.
Copyright 2000-2023 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>.