OPENSSL-ECPARAM(1ossl)

📦
version 3.5.9 · 8 versions
, in alpine 3.23, alpine 3.24

🌸 openssl-ecparam(1ossl) — bestie edition 🌸

okay so this is the openssl-ecparam page from the OpenSSL manual (manual name 1ossl, the OpenSSL one, hi 💖) — EC parameter manipulation and generation, and yes we're gonna get into it.

✨ NAME ✨

openssl-ecparam — EC parameter manipulation and generation. that's it, that's the whole vibe. 💅

🎀 SYNOPSIS 🎀

openssl ecparam [-help] [-inform DER|PEM] [-outform DER|PEM] [-in
filename] [-out filename] [-noout] [-text] [-check] [-check_named]
[-name arg] [-list_curves] [-conv_form arg] [-param_enc arg] [-no_seed]
[-genkey] [-engine id] [-rand files] [-writerand file] [-provider name]
[-provider-path path] [-provparam [name:]key=value] [-propquery propq]

look at all those flags. she's got range. 👑

🦋 DESCRIPTION 🦋

so this command is the one you call when you need to manipulate or generate EC parameter files. main character energy, honestly.

here's the tea though, and it's important: OpenSSL is currently not able to generate new groups, which means this command can only create EC parameters from known (named) curves. so like, it's not out here inventing brand new curves from scratch — no cap, it can't. it works from the named ones that already exist. 🫶

💜 OPTIONS 💜

  • -help — prints out a usage message. the classic "what do I even do here" button. ✨
  • -inform DER|PEM — the EC parameters input format. unspecified by default (so, like, no assumption made 👀). see openssl-format-options(1) for the details.
  • -outform DER|PEM — the EC parameters output format, and the default is PEM. see openssl-format-options(1) for details.

parameters are encoded as EcpkParameters as specified in IETF RFC 3279. love a standards-compliant moment.

  • -in filename — specifies the input file to read parameters from, or standard input if you don't pass this option. default behavior stays lowkey.
  • -out filename — specifies the output filename for parameters. standard output is used if this option isn't present. and yes, the output filename can be the same as the input filename — which leads to replacing the file contents. ⚠️ but note that file I/O is not atomic: the output file gets truncated and then written. so if something goes wrong in between, that file is just... gone. be so fr when picking filenames, bestie. 💀
  • -noout — inhibits the output of the encoded version of the parameters. she's shy, she's not showing the encoded bytes today. 🙈
  • -text — prints out the EC parameters in human readable form. bless. 🌸
  • -check — validate the elliptic curve parameters. doing a vibe check on the curve. ✅
  • -check_named — validate the elliptic name curve parameters by checking if the curve parameters match any built-in curves. like, does this curve already live here or not 🧚
  • -name arg — use the EC parameters with the specified 'short' name. pro tip: use -list_curves to get a list of all currently implemented EC parameters. iykyk.
  • -list_curves — prints out a list of all currently implemented EC parameters names and exits. window shopping for curves, iconic. 👑
  • -conv_form arg — specifies how the points on the elliptic curve are converted into octet strings. possible values: compressed, uncompressed (the default value) and hybrid. for more info on point conversion forms, go read the X9.62 standard. Note: due to patent issues the compressed option is disabled by default for binary curves and can be enabled by defining the preprocessor macro OPENSSL_EC_BIN_PT_COMP at compile time. yeah. patents. whole thing. 😭
  • -param_enc arg — specifies how the elliptic curve parameters are encoded. possible values are: named_curve, i.e. the ec parameters are specified by an OID, or explicit where the ec parameters are explicitly given (see RFC 3279 for the definition of the EC parameters structures). the default value is named_curve. Note: the implicitlyCA alternative, as specified in RFC 3279, is currently not implemented in OpenSSL. not us, not today. 🙅
  • -no_seed — inhibits the 'seed' for the parameter generation from being included in the ECParameters structure (see RFC 3279). no seed, no problem. 🌱
  • -genkey — will generate an EC private key using the specified parameters. a little treat. a little key. 🔥
  • -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. chaos, but documented chaos. 🎲
  • -provider name
  • -provider-path path
  • -provparam [name:]key=value
  • -propquery propq — see "Provider Options" in openssl(1), provider(7), and property(7).

ngl, there's something you should know: the openssl-genpkey(1) and openssl-pkeyparam(1) commands are capable of performing all the operations this command can, as well as supporting other public key types. so like... she's the versatile one. 👀✨

🌈 EXAMPLES 🌈

the documentation for the openssl-genpkey(1) and openssl-pkeyparam(1) commands contains examples equivalent to the ones listed here, fyi.

to create EC parameters with the group 'prime192v1':

openssl ecparam -out ec_param.pem -name prime192v1

to create EC parameters with explicit parameters:

openssl ecparam -out ec_param.pem -name prime192v1 -param_enc explicit

to validate given EC parameters:

openssl ecparam -in ec_param.pem -check

to create EC parameters and a private key:

openssl ecparam -out ec_key.pem -name prime192v1 -genkey

to change the point encoding to 'compressed':

openssl ecparam -in ec_in.pem -out ec_out.pem -conv_form compressed

to print out the EC parameters to standard output:

openssl ecparam -in ec_param.pem -noout -text

⭐ SEE ALSO ⭐

openssl(1), openssl-pkeyparam(1), openssl-genpkey(1), openssl-ec(1), openssl-dsaparam(1)

🧚 HISTORY 🧚

  • the -engine option was deprecated in OpenSSL 3.0.
  • the -C option was removed in OpenSSL 3.0. rest in peace to a real one 🕯️

Copyright 2003-2021 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>.

okay that's the whole page, and shoutout to the footer details so you know exactly where this came from: this was 3.5.9, dated 2026-09-29, page OPENSSL-ECPARAM(1ossl) — mwah, slay, periodt. 🫶💅✨

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