Cryptography and SSL/TLS Toolkit



pkeyutl - public key algorithm utility


openssl pkeyutl [-help] [-in file] [-out file] [-sigfile file] [-inkey file] [-keyform PEM|DER|ENGINE] [-passin arg] [-peerkey file] [-peerform PEM|DER|ENGINE] [-pubin] [-certin] [-rev] [-sign] [-verify] [-verifyrecover] [-encrypt] [-decrypt] [-derive] [-kdf algorithm] [-kdflen length] [-pkeyopt opt:value] [-hexdump] [-asn1parse] [-engine id] [-engine_impl]


The pkeyutl command can be used to perform public key operations using any supported algorithm.



Print out a usage message.

-in filename

This specifies the input filename to read data from or standard input if this option is not specified.

-out filename

specifies the output filename to write to or standard output by default.

-sigfile file

Signature file, required for verify operations only

-inkey file

the input key file, by default it should be a private key.


the key format PEM, DER or ENGINE. Default is PEM.

-passin arg

the input key password source. For more information about the format of arg see the PASS PHRASE ARGUMENTS section in openssl.

-peerkey file

the peer key file, used by key derivation (agreement) operations.

-peerform PEM|DER|ENGINE

the peer key format PEM, DER or ENGINE. Default is PEM.


the input file is a public key.


the input is a certificate containing a public key.


reverse the order of the input buffer. This is useful for some libraries (such as CryptoAPI) which represent the buffer in little endian format.


sign the input data and output the signed result. This requires a private key.


verify the input data against the signature file and indicate if the verification succeeded or failed.


verify the input data and output the recovered data.


encrypt the input data using a public key.


decrypt the input data using a private key.


derive a shared secret using the peer key.

-kdf algorithm

Use key derivation function algorithm. The supported algorithms are at present TLS1-PRF and HKDF. Note: additional parameters and the KDF output length will normally have to be set for this to work. See EVP_PKEY_HKDF and EVP_PKEY_TLS1_PRF for the supported string parameters of each algorithm.

-kdflen length

Set the output length for KDF.

-pkeyopt opt:value

Public key options specified as opt:value. See NOTES below for more details.


hex dump the output data.


asn1parse the output data, this is useful when combined with the -verifyrecover option when an ASN1 structure is signed.

-engine id

specifying an engine (by its unique id string) will cause pkeyutl 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.


When used with the -engine option, it specifies to also use engine id for crypto operations.


The operations and options supported vary according to the key algorithm and its implementation. The OpenSSL operations and options are indicated below.

Unless otherwise mentioned all algorithms support the digest:alg option which specifies the digest in use for sign, verify and verifyrecover operations. The value alg should represent a digest name as used in the EVP_get_digestbyname() function for example sha1. This value is used only for sanity-checking the lengths of data passed in to the pkeyutl and for creating the structures that make up the signature (e.g. DigestInfo in RSASSA PKCS#1 v1.5 signatures). In case of RSA, ECDSA and DSA signatures, this utility will not perform hashing on input data but rather use the data directly as input of signature algorithm. Depending on key type, signature type and mode of padding, the maximum acceptable lengths of input data differ. In general, with RSA the signed data can't be longer than the key modulus, in case of ECDSA and DSA the data shouldn't be longer than field size, otherwise it will be silently truncated to field size.

In other words, if the value of digest is sha1 the input should be 20 bytes long binary encoding of SHA-1 hash function output.


The RSA algorithm generally supports the encrypt, decrypt, sign, verify and verifyrecover operations. However, some padding modes support only a subset of these operations. The following additional pkeyopt values are supported:


This sets the RSA padding mode. Acceptable values for mode are pkcs1 for PKCS#1 padding, sslv23 for SSLv23 padding, none for no padding, oaep for OAEP mode, x931 for X9.31 mode and pss for PSS.

In PKCS#1 padding if the message digest is not set then the supplied data is signed or verified directly instead of using a DigestInfo structure. If a digest is set then the a DigestInfo structure is used and its the length must correspond to the digest type.

For oaep mode only encryption and decryption is supported.

For x931 if the digest type is set it is used to format the block data otherwise the first byte is used to specify the X9.31 digest ID. Sign, verify and verifyrecover are can be performed in this mode.

For pss mode only sign and verify are supported and the digest type must be specified.


For pss mode only this option specifies the salt length. Two special values are supported: -1 sets the salt length to the digest length. When signing -2 sets the salt length to the maximum permissible value. When verifying -2 causes the salt length to be automatically determined based on the PSS block structure.


The DSA algorithm supports signing and verification operations only. Currently there are no additional options other than digest. Only the SHA1 digest can be used and this digest is assumed by default.


The DH algorithm only supports the derivation operation and no additional options.


The EC algorithm supports sign, verify and derive operations. The sign and verify operations use ECDSA and derive uses ECDH. Currently there are no additional options other than digest. Only the SHA1 digest can be used and this digest is assumed by default.


The X25519 algorithm supports key derivation only. Currently there are no additional options.


Sign some data using a private key:

 openssl pkeyutl -sign -in file -inkey key.pem -out sig

Recover the signed data (e.g. if an RSA key is used):

 openssl pkeyutl -verifyrecover -in sig -inkey key.pem

Verify the signature (e.g. a DSA key):

 openssl pkeyutl -verify -in file -sigfile sig -inkey key.pem

Sign data using a message digest value (this is currently only valid for RSA):

 openssl pkeyutl -sign -in file -inkey key.pem -out sig -pkeyopt digest:sha256

Derive a shared secret value:

 openssl pkeyutl -derive -inkey key.pem -peerkey pubkey.pem -out secret

Hexdump 48 bytes of TLS1 PRF using digest SHA256 and shared secret and seed consisting of the single byte 0xFF:

 openssl pkeyutl -kdf TLS1-PRF -kdflen 48 -pkeyopt md:SHA256 \
    -pkeyopt hexsecret:ff -pkeyopt hexseed:ff -hexdump


genpkey, pkey, rsautl dgst, rsa, genrsa, EVP_PKEY_HKDF, EVP_PKEY_TLS1_PRF

Copyright 2006-2016 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