OPENSSL-DHPARAM(1ossl)

📦
version 15.1 · 2 versions
, in freebsd 15.1

Okay bestie, welcome to the OPENSSL-DHPARAM(1ossl) page — OpenSSL manual, section 1ossl. This is where we talk about DH parameter manipulation and generation, and yes, she ate. 💅

🌸 NAME 🌸

openssl-dhparam — DH parameter manipulation and generation. That's the whole assignment, and we're gonna do it cute and correct. 🫶

✨ 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. Literally that's the job, bestie.

Also: see "EXAMPLES" in openssl-genpkey(1) for examples on how to generate a key using a named safe prime group without generating intermediate parameters. iykyk

👑 OPTIONS 👑

  • -help — Prints out a usage message. Helpful queen behavior.
  • -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. Formatting matters, bestie.
  • -in filename — This specifies the input file to read parameters from, or standard input if this option is not specified. No -in? Then stdin is the main character.
  • -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. So yeah, same-name output replaces stuff — be aware.
  • -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. Much faster, yes, but listen:

Beware: 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. Vibe check for your params.
  • -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. Pick your generator era.
  • 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. Numbers, bestie: 512 to 10000, default 2048 when a generator is around.
  • -noout — This option inhibits the output of the encoded version of the parameters. No encoded output, periodt.
  • -text — This option prints out the DH parameters in human readable form. Human-readable form is the moment.
  • -engine id — See "Engine Options" in openssl(1). This option is deprecated. Deprecated, so don't come for me.
  • -rand files, -writerand file — See "Random State Options" in openssl(1) for details. Randomness details live over there.
  • -provider name, -provider-path path, -provparam [name:]key=value, -propquery propq — See "Provider Options" in openssl(1), provider(7), and property(7). Provider lore, unlocked elsewhere.
  • -verbose — This option enables the output of progress messages, which is handy when running commands interactively that may take a long time to execute. Progress messages for the long-haul commands.
  • -quiet — This option suppresses the output of progress messages, which may be undesirable in batch scripts or pipelines. Quiet mode: great for scripts, maybe not for watching progress.

🦋 NOTES 🦋

This command replaces the dh and gendh commands of previous releases. New name, same replacement energy.

🌈 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 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>.

That's the page, bestie — version 3.5.6, dated 2026-04-07. Stay encrypted and iconic. 💖

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