OPENSSL-PKEYUTL(1)

NAME
openssl-pkeyutl - public key algorithm command

SYNOPSIS
openssl pkeyutl [-help] [-in file] [-rawin] [-digest algorithm] [-out file] [-sigfile file] [-inkey filename|uri] [-keyform DER|PEM|P12|ENGINE] [-passin arg] [-peerkey file] [-peerform DER|PEM|P12|ENGINE] [-pubin] [-certin] [-rev] [-sign] [-verify] [-verifyrecover] [-encrypt] [-decrypt] [-derive] [-kdf algorithm] [-kdflen length] [-pkeyopt opt:value] [-pkeyopt_passin opt[:passarg]] [-hexdump] [-asn1parse] [-engine id] [-engine_impl] [-rand files] [-writerand file] [-provider name] [-provider-path path] [-propquery propq] [-config configfile]

DESCRIPTION
This command can be used to perform low-level public key operations using any supported algorithm.

By default the signing operation (see -sign option) is assumed.

OPTIONS

-help
    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.

-rawin
    This indicates that the signature or verification input data is raw data, which is not hashed by any message digest algorithm. Except with EdDSA, the user can specify a digest algorithm by using the -digest option. For signature algorithms like RSA, DSA and ECDSA, the default digest algorithm is SHA-256. For SM2, it is SM3.

    This option can only be used with -sign and -verify. For EdDSA (the Ed25519 and Ed448 algorithms) this option is required.

-digest algorithm
    This option can only be used with -sign and -verify. It specifies the digest algorithm that is used to hash the input data before signing or verifying it with the input key. This option could be omitted if the signature algorithm does not require preprocessing the input through a pluggable hash function before signing (for instance, EdDSA). If this option is omitted but the signature algorithm requires one and the -rawin option is given, a default value will be used (see -rawin for details). If this option is present, then the -rawin option is required.

    At this time, HashEdDSA (the ph or "prehash" variant of EdDSA) is not supported, so the -digest option cannot be used with EdDSA.

-out filename
    Specifies the output filename to write to or standard output by default.

-sigfile file
    Signature file, required and allowed for -verify operations only

-inkey filename|uri
    The input key, by default it should be a private key.

-keyform DER|PEM|P12|ENGINE
    The key format; unspecified by default. See openssl-format-options(1) for details.

-passin arg
    The input key password source. For more information about the format of arg see openssl-passphrase-options(1).

-peerkey file
    The peer key file, used by key derivation (agreement) operations.

-peerform DER|PEM|P12|ENGINE
    The peer key format; unspecified by default. See openssl-format-options(1) for details.

-pubin
    By default a private key is read from the key input. With this option a public key is read instead. If the input contains no public key but a private key, its public part is used.

-certin
    The input is a certificate containing a public key.

-rev
    Reverse the order of the input buffer. This is useful for some libraries (such as CryptoAPI) which represent the buffer in little-endian format. This cannot be used in conjunction with -rawin.

-sign
    Sign the input data and output the signed result. This requires a private key. Using a message digest operation along with this is recommended, when applicable, see the -rawin and -digest options for details. Otherwise, the input data given with the -in option is assumed to already be a digest, but this may then require an additional -pkeyopt "digest:"md in some cases (e.g., RSA with the default PKCS#1 padding mode). Even for other algorithms like ECDSA, where the additional -pkeyopt option does not affect signature output, it is recommended, as it enables checking that the input length is consistent with the intended digest.

-verify
    Verify the input data against the signature given with the -sigfile option and indicate if the verification succeeded or failed. The input data given with the -in option is assumed to be a hash value unless the -rawin option is specified or implied. With raw data, when a digest algorithm is applicable, though it may be inferred from the signature or take a default value, it should also be specified.

-verifyrecover
    Verify the given signature and output the recovered data (signature payload). For example, in case of RSA PKCS#1 the recovered data is the EMSA-PKCS-v1_5 DER encoding of the digest algorithm OID and value as specified in RFC8017 Section 9.2 <https://datatracker.ietf.org/doc/html/rfc8017#section-9.2>.

    Note that here the input given with the -in option is not a signature input (as with the -sign and -verify options) but a signature output value, typically produced using the -sign option.

    This option is available only for use with RSA keys.

-encrypt
    Encrypt the input data using a public key.

-decrypt
    Decrypt the input data using a private key.

-derive
    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_CTX_set_hkdf_md(3) and EVP_PKEY_CTX_set_tls1_prf_md(3) 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.

-pkeyopt_passin opt[:passarg]
    Allows reading a public key option opt from stdin or a password source. If only opt is specified, the user will be prompted to enter a password on stdin. Alternatively, passarg can be specified which can be any value supported by openssl-passphrase-options(1).

-hexdump
    hex dump the output data.

-asn1parse
    Parse the ASN.1 output data to check its DER encoding and print any errors. When combined with the -verifyrecover option, this may be useful only in case an ASN.1 DER-encoded structure had been signed directly (without hashing it).

-engine id
    See "Engine Options" in openssl(1). This option is deprecated.

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

-rand files, -writerand file
    See "Random State Options" in openssl(1) for details.

-provider name
-provider-path path
-propquery propq
    See "Provider Options" in openssl(1), provider(7), and property(7).

-config configfile
    See "Configuration Option" in openssl(1).

NOTES
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 the signing and verification operations. The value alg should represent a digest name as used in the EVP_get_digestbyname() function for example sha1. This value is not used to hash the input data. It is used (by some algorithms) for sanity-checking the lengths of data passed in and for creating the structures that make up the signature (e.g. DigestInfo in RSASSA PKCS#1 v1.5 signatures).

This command does not hash the input data (except where -rawin is used) but rather it will use the data directly as input to the signature algorithm. Depending on the key type, signature type, and mode of padding, the maximum acceptable lengths of input data differ. The signed data can't be longer than the key modulus with RSA. In case of ECDSA and DSA the data shouldn't be longer than the field size, otherwise it will be silently truncated to the field size. In any event the input size must not be larger than the largest supported digest size.

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

RSA ALGORITHM
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:

rsa_padding_mode:mode
    This sets the RSA padding mode. Acceptable values for mode are pkcs1 for PKCS#1 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 DigestInfo structure is used and its length must correspond to the digest type.

    Note, for pkcs1 padding, as a protection against the Bleichenbacher attack, the decryption will not fail in case of padding check failures. Use none and manual inspection of the decrypted message to verify if the decrypted value has correct PKCS#1 v1.5 padding.

    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.

rsa_pss_saltlen:len
    For pss mode only this option specifies the salt length. Three special values are supported: digest sets the salt length to the digest length, max sets the salt length to the maximum permissible value. When verifying auto causes the salt length to be automatically determined based on the PSS block structure.

rsa_mgf1_md:digest
    For PSS and OAEP padding sets the MGF1 digest. If the MGF1 digest is not explicitly set in PSS mode then the signing digest is used.

rsa_oaep_md:digest
    Sets the digest used for the OAEP hash function. If not explicitly set then SHA1 is used.

rsa_pkcs1_implicit_rejection:flag
    Disables (when set to 0) or enables (when set to 1) the use of implicit rejection with PKCS#1 v1.5 decryption. When enabled (the default), as a protection against Bleichenbacher attack, the library will generate a deterministic random plaintext that it will return to the caller in case of padding check failure. When disabled, it's the callers' responsibility to handle the returned errors in a side-channel free manner.

RSA-PSS ALGORITHM
The RSA-PSS algorithm is a restricted version of the RSA algorithm which only supports the sign and verify operations with PSS padding. The following additional -pkeyopt values are supported:

rsa_padding_mode:mode, rsa_pss_saltlen:len, rsa_mgf1_md:digest
    These have the same meaning as the RSA algorithm with some additional restrictions. The padding mode can only be set to pss which is the default value.

    If the key has parameter restrictions then the digest, MGF1 digest and salt length are set to the values specified in the parameters. The digest and MG cannot be changed and the salt length cannot be set to a value less than the minimum restriction.

DSA ALGORITHM
The DSA algorithm supports signing and verification operations only. Currently there are no additional -pkeyopt options other than digest. The SHA1 digest is assumed by default.

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

EC ALGORITHM
The EC algorithm supports sign, verify and derive operations. The sign and verify operations use ECDSA and derive uses ECDH. SHA1 is assumed by default for the -pkeyopt digest option.

X25519 AND X448 ALGORITHMS
The X25519 and X448 algorithms support key derivation only. Currently there are no additional options.

ED25519 AND ED448 ALGORITHMS
These algorithms only support signing and verifying. OpenSSL only implements the "pure" variants of these algorithms so raw data can be passed directly to them without hashing them first. The option -rawin must be used with these algorithms with no -digest specified. Additionally OpenSSL only supports "oneshot" operation with these algorithms. This means that the entire file to be signed/verified must be read into memory before processing it. Signing or Verifying very large files should be avoided. Additionally the size of the file must be known for this to work. If the size of the file cannot be determined (for example if the input is stdin) then the sign or verify operation will fail.

SM2
The SM2 algorithm supports sign, verify, encrypt and decrypt operations. For the sign and verify operations, SM2 requires an Distinguishing ID string to be passed in. The following -pkeyopt value is supported:

distid:string
    This sets the ID string used in SM2 sign or verify operations. While verifying an SM2 signature, the ID string must be the same one used when signing the data. Otherwise the verification will fail.

hexdistid:hex_string
    This sets the ID string used in SM2 sign or verify operations. While verifying an SM2 signature, the ID string must be the same one used when signing the data. Otherwise the verification will fail. The ID string provided with this option should be a valid hexadecimal value.

EXAMPLES
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

Derive a key using scrypt where the password is read from command line:

 openssl pkeyutl -kdf scrypt -kdflen 16 -pkeyopt_passin pass \
    -pkeyopt hexsalt:aabbcc -pkeyopt N:16384 -pkeyopt r:8 -pkeyopt p:1

Derive using the same algorithm, but read key from environment variable MYPASS:

 openssl pkeyutl -kdf scrypt -kdflen 16 -pkeyopt_passin pass:env:MYPASS \
    -pkeyopt hexsalt:aabbcc -pkeyopt N:16384 -pkeyopt r:8 -pkeyopt p:1

Sign some data using an SM2(7) private key and a specific ID:

 openssl pkeyutl -sign -in file -inkey sm2.key -out sig -rawin -digest sm3 \
    -pkeyopt distid:someid

Verify some data using an SM2(7) certificate and a specific ID:

 openssl pkeyutl -verify -certin -in file -inkey sm2.cert -sigfile sig \
    -rawin -digest sm3 -pkeyopt distid:someid

Decrypt some data using a private key with OAEP padding using SHA256:

 openssl pkeyutl -decrypt -in file -inkey key.pem -out secret \
    -pkeyopt rsa_padding_mode:oaep -pkeyopt rsa_oaep_md:sha256

SEE ALSO
openssl(1), openssl-genpkey(1), openssl-pkey(1), openssl-rsautl(1) openssl-dgst(1), openssl-rsa(1), openssl-genrsa(1), openssl-kdf(1) EVP_PKEY_CTX_set_hkdf_md(3), EVP_PKEY_CTX_set_tls1_prf_md(3),

HISTORY
The -engine option was deprecated in OpenSSL 3.0.

COPYRIGHT
Copyright 2006-2023 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>.