NAME

openssl-pkeyutl - asymmetric key command

SYNOPSIS

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

DESCRIPTION

This command can be used to perform low-level operations on asymmetric (public or private) keys 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 SHA256. 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 implied since OpenSSL 3.5, and required in earlier versions.

The -digest option implies -rawin since OpenSSL 3.5.

-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 implied since OpenSSL 3.5, and required in earlier versions.

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.

-secret filename

Specifies the shared-secret output filename for when performing encapsulation via the -encap option or decapsulation via the -decap option. The -encap option also produces a separate (public) ciphertext output which is by default written to standard output, but being binary non-text data, is typically also redirected to a file selected via the -out option.

-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).

-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 own private (EC)DH key and peer key.

-peerkey file

File containing the peer public or private (EC)DH key to use with the key derivation (agreement) operation. Its type must match the type of the own private key given with -inkey.

-peerform DER|PEM|P12|ENGINE

The peer key format; unspecified by default. See openssl-format-options(1) for details.

-encap

Use a Key Encapsulation Mechanism (KEM) to encapsulate a shared-secret to a peer's public key. The encapsulated result (or ciphertext, non-text binary data) is written to standard output by default, or else to the file specified with -out. The -secret option must also be provided to specify the output file for the derived shared-secret value generated in the encapsulation process. Encapsulation is supported with a number of public key algorithms, currently: ML-KEM, X25519, X448, and EC. The ECX and EC algorithms use the RFC9180 <https://www.rfc-editor.org/rfc/rfc9180> DHKEM construction. Encapsulation is also supported with RSA keys via the RSASVE construction.

At the API level, encapsulation and decapsulation are also supported for a few hybrid ECDHE (no DHKEM) plus ML-KEM algorithms, but these are intended primarily for use with TLS and should not be used standalone. There are in any case no standard public and private key formats for the hybrid algorithms, so it is not possible to provide the required key material.

-decap

Decode an encapsulated secret, with the use of a -private key, to derive the same shared-secret as that obtained when the secret was encapsulated to the corresponding public key. The encapsulated secret is by default read from the standard input, or else from the file specified with -in. The derived shared-secret is written to the file specified with the -secret option, which must also be provided. Decapsulation is supported with a number of public key algorithms, currently: ML-KEM, X25519, X448, and EC. The ECX and EC algorithms use the RFC9180 <https://www.rfc-editor.org/rfc/rfc9180> DHKEM construction. Decapsulation is also supported with RSA keys via the RSASVE construction.

-kemop mode

This option is used with the -encap/-decap commands and specifies the KEM mode specific for the key algorithm when there is no default way to encapsulate and decapsulate shared secrets with the chosen key type. All the supported algorithms presently support only their default mode, and this option, though available, is not required.

-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 in case an ASN.1 DER-encoded structure had been signed directly (without hashing it) and when checking a signature in PKCS#1 v1.5 format, which has a DER encoding.

-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

-provparam [name:]key=value

-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, the -pkeyopt option supports for all public-key types the "digest:"alg argument, 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 sha256. 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).

For instance, if the value of the -pkeyopt option "digest" argument is sha256, the signature or verification input should be the 32 bytes long binary value of the SHA256 hash function output.

Unless -rawin is used or implied, this command does not hash the input data 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 sensible lengths of input data differ. With RSA the signed data cannot be longer than the key modulus. In case of ECDSA and DSA the data should not 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 output size EVP_MAX_MD_SIZE, which currently is 64 bytes.

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 SHA256 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 SHA256 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. SHA256 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.

ML-DSA-44, ML-DSA-65 AND ML-DSA-87 ALGORITHMS

The ML-DSA algorithms are post-quantum signature algorithms that support signing and verification of "raw" messages. No preliminary hashing is performed. When using ML-DSA with pkeyutl, the following options are available:

-sign

Sign the input data using an ML-DSA private key. For example:

  $ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig
    

-verify

Verify the signature using an ML-DSA public key. For example:

  $ openssl pkeyutl -verify -in file.txt -inkey mldsa65.pem -sigfile sig
    

-pkeyopt opt:value

Additional options for ML-DSA signing and verification:

context-string:string

Specifies a context string for both signing and verification operations. The context string must be the same for verification to succeed. For example:

  $ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt context-string:mycontext
  $ openssl pkeyutl -verify -in file.txt -inkey mldsa65.pem -sigfile sig -pkeyopt context-string:mycontext
    

hexcontext-string:string

Specifies a context string in hex format, allowing binary control values. For example:

  $ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt hexcontext-string:6d79636f6e74657874
    

The signing operation supports a deterministic:bool option, with bool set to 1 if a deterministic signature is to be generated with a fixed all zero random input. By default, or if the bool is 0 a random entropy value is used. A deterministic result can also be obtained by specifying an explicit entropy value via the hextest-entropy:value parameter. Deterministic ML-DSA signing should only be used in tests.

See EVP_SIGNATURE-ML-DSA(7) for additional details about the ML-DSA algorithms and their implementation.

ML-KEM-512, ML-KEM-768 AND ML-KEM-1024 ALGORITHMS

The ML-KEM algorithms support encapsulation and decapsulation only. The encapsulation operation supports a hexikme:entropy option, with entropy the 64 hexadecimal digit encoding of a 32-byte value. This should only be used in tests, known or leaked values of the option may compromise the generated shared secret.

See EVP_KEM-ML-KEM(7) for additional detail.

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. 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

Create an ML-DSA key pair and sign data with a specific context string:

  $ openssl genpkey -algorithm ML-DSA-65 -out mldsa65.pem
  $ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt context-string:example

Verify a signature using ML-DSA with the same context string:

  $ openssl pkeyutl -verify -in file.txt -inkey mldsa65.pem -sigfile sig -pkeyopt context-string:example

Generate an ML-KEM key pair and use it for encapsulation:

  $ openssl genpkey -algorithm ML-KEM-768 -out mlkem768.pem
  $ openssl pkey -in mlkem768.pem -pubout -out mlkem768_pub.pem
  $ openssl pkeyutl -encap -inkey mlkem768_pub.pem -pubin -out ciphertext -secret shared_secret.bin

Decapsulate a shared secret using an ML-KEM private key:

  $ openssl pkeyutl -decap -inkey mlkem768.pem -in ciphertext -secret decapsulated_secret.bin

Create an SLH-DSA key pair and sign data:

  $ openssl genpkey -algorithm SLH-DSA-SHA2-128s -out slh-dsa.pem
  $ openssl pkeyutl -sign -in file.txt -inkey slh-dsa.pem -out sig

Verify a signature using SLH-DSA:

  $ openssl pkeyutl -verify -in file.txt -inkey slh-dsa.pem -sigfile sig

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

Since OpenSSL 3.5, the -digest option implies -rawin, and these two options are no longer required when signing or verifying with an Ed25519 or Ed448 key.

Also since OpenSSL 3.5, the -kemop option is no longer required for any of the supported algorithms, the only supported mode is now the default.

The -engine option was deprecated in OpenSSL 3.0.

COPYRIGHT

Copyright 2006-2026 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>.