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openssl-ecparam, ecparam - EC parameter manipulation and generation


openssl ecparam [-help] [-inform DER|PEM] [-outform DER|PEM] [-in filename] [-out filename] [-noout] [-text] [-C] [-check] [-name arg] [-list_curves] [-conv_form arg] [-param_enc arg] [-no_seed] [-rand file...] [-writerand file] [-genkey] [-engine id]


This command is used to manipulate or generate EC parameter files.


Print out a usage message.
This specifies the input format. The DER option uses an ASN.1 DER encoded form compatible with RFC 3279 EcpkParameters. The PEM form is the default format: it consists of the DER format base64 encoded with additional header and footer lines.
This specifies the output format, the options have the same meaning and default as the -inform option.
This specifies the input filename to read parameters from or standard input if this option is not specified.
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.
This option inhibits the output of the encoded version of the parameters.
This option prints out the EC parameters in human readable form.
This option converts the EC parameters into C code. The parameters can then be loaded by calling the get_ec_group_XXX() function.
Validate the elliptic curve parameters.
Use the EC parameters with the specified 'short' name. Use -list_curves to get a list of all currently implemented EC parameters.
If this options is specified ecparam will print out a list of all currently implemented EC parameters names and exit.
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.
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.
This option inhibits that the 'seed' for the parameter generation is included in the ECParameters structure (see RFC 3279).
This option will generate an EC private key using the specified parameters.
A file or files containing random data used to seed the random number generator. Multiple files can be specified separated by an OS-dependent character. The separator is ; for MS-Windows, , for OpenVMS, and : for all others.
[-writerand file]
Writes random data to the specified file upon exit. This can be used with a subsequent -rand flag.
Specifying an engine (by its unique id string) will cause ecparam to attempt to obtain a functional reference to the specified engine, thus initialising it if needed. The engine will then be set as the default for all available algorithms.


PEM format EC parameters use the header and footer lines:


OpenSSL is currently not able to generate new groups and therefore ecparam can only create EC parameters from known (named) curves.


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


ec(1), dsaparam(1)


Copyright 2003-2018 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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 <>.

2022-06-24 1.1.1n