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>.

3.5.0                                              2025-06-04                              OPENSSL-ECPARAM(1SSL)