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Section: OpenSSL (1)
Updated: 2015-01-20
Index Return to Main Contents


ec - EC key processing  


openssl ec [-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] [-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' ( To convert a OpenSSL EC private key into the PKCS#8 private key format use the pkcs8 command.  


-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 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 the PASS PHRASE ARGUMENTS section 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 the PASS PHRASE ARGUMENTS section in openssl(1).
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.
prints out the public, private key components and parameters.
this option prevents output of the encoded version of the key.
this option prints out the value of the public key component of the key.
by default a private key is read from the input file: with this option a public key is read instead.
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.
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.
-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:


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

 -----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



ecparam(1), dsa(1), rsa(1)  


The ec command was first introduced in OpenSSL 0.9.8.  


Nils Larsch for the OpenSSL project (




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