OPENSSL-ECPARAM(1SSL) OpenSSL OPENSSL-ECPARAM(1SSL)
NAME
openssl-ecparam - EC parameter manipulation and generation
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]
DESCRIPTION
This command is used to manipulate or generate EC parameter files.
OpenSSL is currently not able to generate new groups and therefore this
command can only create EC parameters from known (named) curves.
OPTIONS
-help
Print out a usage message.
-inform DER|PEM
The EC parameters input format; unspecified by default. See
openssl-format-options(1) for details.
-outform DER|PEM
The EC parameters output format; the default is PEM. See
openssl-format-options(1) for details.
Parameters are encoded as EcpkParameters as specified in IETF RFC
3279.
-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 filename 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.
-noout
This option inhibits the output of the encoded version of the
parameters.
-text
This option prints out the EC parameters in human readable form.
-check
Validate the elliptic curve parameters.
-check_named
Validate the elliptic name curve parameters by checking if the curve
parameters match any built-in curves.
-name arg
Use the EC parameters with the specified 'short' name. Use
-list_curves to get a list of all currently implemented EC
parameters.
-list_curves
Print out a list of all currently implemented EC parameters names
and exit.
-conv_form arg
This specifies how the points on the elliptic curve are converted
into octet strings. Possible values are: compressed, uncompressed
(the default value) and hybrid. For more information regarding the
point conversion forms please 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.
-param_enc arg
This specifies how the elliptic curve parameters are encoded.
Possible value 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.
-no_seed
This option inhibits that the 'seed' for the parameter generation is
included in the ECParameters structure (see RFC 3279).
-genkey
This option will generate an EC private key using the specified
parameters.
-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).
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.
EXAMPLES
The documentation for the openssl-genpkey(1) and openssl-pkeyparam(1)
commands contains examples equivalent to the ones listed here.
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.
COPYRIGHT
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>.
3.5.4 2025-09-30 OPENSSL-ECPARAM(1SSL)
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