OPENSSL-PKEYUTL(1ossl) OpenSSL OPENSSL-PKEYUTL(1ossl)
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, X449, 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.
SLH-DSA ALGORITHMS
The SLH-DSA algorithms (SLH-DSA-SHA2-128s, SLH-DSA-SHA2-128f,
SLH-DSA-SHA2-192s, SLH-DSA-SHA2-192f, SLH-DSA-SHA2-256s,
SLH-DSA-SHA2-256f) are post-quantum signature algorithms. When using
SLH-DSA with pkeyutl, the following options are available:
-sign
Sign the input data using an SLH-DSA private key. For example:
$ openssl pkeyutl -sign -in file.txt -inkey slhdsa.pem -out sig
-verify
Verify the signature using an SLH-DSA public key. For example:
$ openssl pkeyutl -verify -in file.txt -inkey slhdsa.pem -sigfile sig
See EVP_PKEY-SLH-DSA(7) and EVP_SIGNATURE-SLH-DSA(7) for additional
details about the SLH-DSA algorithm and its implementation.
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:
message-encoding:value
Specifies the message encoding mode used for signing. This
controls how the input message is processed before signing.
Valid values are described in EVP_SIGNATURE-ML-DSA(7). For
example:
$ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt message-encoding:1
test-entropy:value
Specifies a test entropy value for deterministic signing. For
example:
$ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt test-entropy:abcdefghijklmnopqrstuvwxyz012345
hextest-entropy:value
Specifies a test entropy value in hex format. For example:
$ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt hextest-entropy:000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f
deterministic:value
Enables deterministic signing. For example:
$ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt deterministic:1
mu:value
Specifies the mu parameter. For example:
$ echo -n "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef" >file.txt
$ openssl pkeyutl -sign -in file.txt -inkey mldsa65.pem -out sig -pkeyopt mu:1
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 2006-2025 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>.
3.5.1 2025-07-02 OPENSSL-PKEYUTL(1ossl)
openssl 3.5.1 - Generated Fri Aug 1 12:36:42 CDT 2025