ec.1s

openssl ec [-help] [-inform PEM|DER] [-outform PEM|DER] [-in filename] [-passin arg] [-out filename] [-passout arg] [-des] [-des3] [-idea] [-text] [-noout] [-param_out] [-pubin] [-pubout] [-conv_form arg] [-param_enc arg] [-no_public] [-check] [-engine id]

The ec command processes EC keys. They can be converted between various forms and their components printed out. Note OpenSSL uses the private key format specified in 'SEC 1: Elliptic Curve Cryptography' (http://www.secg.org/). To convert an OpenSSL EC private key into the PKCS#8 private key format use the pkcs8 command.

-help

Print out a usage message.

-inform DER|PEM

This specifies the input format. The DER option with a private key uses an ASN.1 DER encoded SEC1 private key. When used with a public key it uses the SubjectPublicKeyInfo structure as specified in RFC 3280. The PEM form is the default format: it consists of the DER format base64 encoded with additional header and footer lines. In the case of a private key PKCS#8 format is also accepted.

-outform DER|PEM

This specifies the output format, the options have the same meaning and default as the -inform option.

-in filename

This specifies the input filename to read a key from or standard input if this option is not specified. If the key is encrypted a pass phrase will be prompted for.

-passin arg

The input file password source. For more information about the format of arg see Pass Phrase Options in openssl (1).

-out filename

This specifies the output filename to write a key to or standard output by is not specified. If any encryption options are set then a pass phrase will be prompted for. The output filename should not be the same as the input filename.

-passout arg

The output file password source. For more information about the format of arg see Pass Phrase Options in openssl (1).

-des|-des3|-idea

These options encrypt the private key with the DES, triple DES, IDEA or any other cipher supported by OpenSSL before outputting it. A pass phrase is prompted for. If none of these options is specified the key is written in plain text. This means that using the ec utility to read in an encrypted key with no encryption option can be used to remove the pass phrase from a key, or by setting the encryption options it can be use to add or change the pass phrase. These options can only be used with PEM format output files.

-text

Prints out the public, private key components and parameters.

-noout

This option prevents output of the encoded version of the key.

-pubin

By default, a private key is read from the input file. With this option a public key is read instead.

-pubout

By default a private key is output. With this option a public key will be output instead. This option is automatically set if the input is a public key.

-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 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_public

This option omits the public key components from the private key output.

-check

This option checks the consistency of an EC private or public key.

-engine id

Specifying an engine (by its unique id string) will cause ec 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.

The PEM private key format uses the header and footer lines:

-----BEGIN EC PRIVATE KEY----- -----END EC PRIVATE KEY-----

The PEM public key format uses the header and footer lines:

-----BEGIN PUBLIC KEY----- -----END PUBLIC KEY-----

To encrypt a private key using triple DES:

openssl ec -in key.pem -des3 -out keyout.pem

To convert a private key from PEM to DER format:

openssl ec -in key.pem -outform DER -out keyout.der

To print out the components of a private key to standard output:

openssl ec -in key.pem -text -noout

To just output the public part of a private key:

openssl ec -in key.pem -pubout -out pubkey.pem

To change the parameters encoding to explicit:

openssl ec -in key.pem -param_enc explicit -out keyout.pem

To change the point conversion form to compressed:

openssl ec -in key.pem -conv_form compressed -out keyout.pem

Copyright 2003-2021 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 <https://www.openssl.org/source/license.html>.

ecparam (1), dsa (1), rsa (1)