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PROGRAM:

NAME

ecparam - EC parameter manipulation and generation

SYNOPSIS

openssl ecparam [-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(s)] [-genkey] [-engine id]

DESCRIPTION

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

OPTIONS

-inform DER|PEM
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.

-outform DER|PEM
This specifies the output format, the options have the same meaning as the -inform
option.

-in filename
This specifies the input filename 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 should not be the same as the input
filename.

-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.

-C This option converts the EC parameters into C code. The parameters can then be loaded
by calling the get_ec_group_XXX() function.

-check
Validate the elliptic curve parameters.

-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
If this options is specified ecparam will print out a list of all currently
implemented EC parameters names and exit.

-conv_form
This specifies how the points on the elliptic curve are converted into octet strings.
Possible values are: compressed (the default value), uncompressed 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 a 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 a EC private key using the specified parameters.

-rand file(s)
a file or files containing random data used to seed the random number generator, or an
EGD socket (see RAND_egd(3)). Multiple files can be specified separated by a OS-
dependent character. The separator is ; for MS-Windows, , for OpenVMS, and : for all
others.

-engine id
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.

NOTES

PEM format EC parameters use the header and footer lines:

-----BEGIN EC PARAMETERS-----

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

EXAMPLES

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

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