Manual: openssl-dhparam

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] [-verbose] [-quiet] [-2] [-3] [-5] [-engine id] [-rand files] [-writerand file] [-provider name]
       [-provider-path path] [-provparam [name:]key=value] [-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 file to read parameters from or standard input if this option is not specified.

       -out filename
	   This specifies the output file to write parameters to.  Standard output is used if this option  is  not  present.
	   The output filename can be the same as the input filename, which leads to replacing the file contents.  Note that
	   file I/O is not atomic. The output file is truncated and then written.

       -dsaparam
	   If  this  option  is	 used,	DSA  rather than DH parameters are read or created; they are converted to DH format.
	   Otherwise, safe 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.  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
       -provparam [name:]key=value
       -propquery propq
	   See "Provider Options" in openssl(1), provider(7), and property(7).

       -verbose
	   This	 option enables the output of progress messages, which is handy when running commands interactively that may
	   take a long time to execute.

       -quiet
	   This option suppresses the output of progress messages, which may be undesirable in batch scripts or pipelines.

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 2000-2023 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
       .

3.5.5							 2026-01-27				       OPENSSL-DHPARAM(1SSL)