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.\" ========================================================================
.\"
.IX Title "PKEYUTL 1"
.TH PKEYUTL 1 "2026-04-30" "1.0.2k" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
pkeyutl \- public key algorithm utility
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
\&\fBopenssl\fR \fBpkeyutl\fR
[\fB\-in file\fR]
[\fB\-out file\fR]
[\fB\-sigfile file\fR]
[\fB\-inkey file\fR]
[\fB\-keyform PEM|DER\fR]
[\fB\-passin arg\fR]
[\fB\-peerkey file\fR]
[\fB\-peerform PEM|DER\fR]
[\fB\-pubin\fR]
[\fB\-certin\fR]
[\fB\-rev\fR]
[\fB\-sign\fR]
[\fB\-verify\fR]
[\fB\-verifyrecover\fR]
[\fB\-encrypt\fR]
[\fB\-decrypt\fR]
[\fB\-derive\fR]
[\fB\-pkeyopt opt:value\fR]
[\fB\-hexdump\fR]
[\fB\-asn1parse\fR]
[\fB\-engine id\fR]
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \fBpkeyutl\fR command can be used to perform public key operations using
any supported algorithm.
.SH "COMMAND OPTIONS"
.IX Header "COMMAND OPTIONS"
.IP "\fB\-in filename\fR" 4
.IX Item "-in filename"
This specifies the input filename to read data from or standard input
if this option is not specified.
.IP "\fB\-out filename\fR" 4
.IX Item "-out filename"
specifies the output filename to write to or standard output by
default.
.IP "\fB\-inkey file\fR" 4
.IX Item "-inkey file"
the input key file, by default it should be a private key.
.IP "\fB\-keyform PEM|DER\fR" 4
.IX Item "-keyform PEM|DER"
the key format \s-1PEM, DER\s0 or \s-1ENGINE.\s0
.IP "\fB\-passin arg\fR" 4
.IX Item "-passin arg"
the input key password source. For more information about the format of \fBarg\fR
see the \fB\s-1PASS PHRASE ARGUMENTS\s0\fR section in \fIopenssl\fR\|(1).
.IP "\fB\-peerkey file\fR" 4
.IX Item "-peerkey file"
the peer key file, used by key derivation (agreement) operations.
.IP "\fB\-peerform PEM|DER\fR" 4
.IX Item "-peerform PEM|DER"
the peer key format \s-1PEM, DER\s0 or \s-1ENGINE.\s0
.IP "\fB\-engine id\fR" 4
.IX Item "-engine id"
specifying an engine (by its unique \fBid\fR string) will cause \fBpkeyutl\fR
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.
.IP "\fB\-pubin\fR" 4
.IX Item "-pubin"
the input file is a public key.
.IP "\fB\-certin\fR" 4
.IX Item "-certin"
the input is a certificate containing a public key.
.IP "\fB\-rev\fR" 4
.IX Item "-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.
.IP "\fB\-sign\fR" 4
.IX Item "-sign"
sign the input data and output the signed result. This requires
a private key.
.IP "\fB\-verify\fR" 4
.IX Item "-verify"
verify the input data against the signature file and indicate if the
verification succeeded or failed.
.IP "\fB\-verifyrecover\fR" 4
.IX Item "-verifyrecover"
verify the input data and output the recovered data.
.IP "\fB\-encrypt\fR" 4
.IX Item "-encrypt"
encrypt the input data using a public key.
.IP "\fB\-decrypt\fR" 4
.IX Item "-decrypt"
decrypt the input data using a private key.
.IP "\fB\-derive\fR" 4
.IX Item "-derive"
derive a shared secret using the peer key.
.IP "\fB\-hexdump\fR" 4
.IX Item "-hexdump"
hex dump the output data.
.IP "\fB\-asn1parse\fR" 4
.IX Item "-asn1parse"
asn1parse the output data, this is useful when combined with the
\&\fB\-verifyrecover\fR option when an \s-1ASN1\s0 structure is signed.
.SH "NOTES"
.IX Header "NOTES"
The operations and options supported vary according to the key algorithm
and its implementation. The OpenSSL operations and options are indicated below.
.PP
Unless otherwise mentioned all algorithms support the \fBdigest:alg\fR option
which specifies the digest in use for sign, verify and verifyrecover operations.
The value \fBalg\fR should represent a digest name as used in the
\&\fIEVP_get_digestbyname()\fR function for example \fBsha1\fR.
This value is used only for sanity-checking the lengths of data passed in to
the \fBpkeyutl\fR and for creating the structures that make up the signature
(e.g. \fBDigestInfo\fR in \s-1RSASSA\s0 PKCS#1 v1.5 signatures).
In case of \s-1RSA, ECDSA\s0 and \s-1DSA\s0 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 \s-1RSA\s0 the signed data can't be longer than the key modulus, in case of \s-1ECDSA\s0
and \s-1DSA\s0 the data shouldn't be longer than field size, otherwise it will be
silently truncated to field size.
.PP
In other words, if the value of digest is \fBsha1\fR the input should be 20 bytes
long binary encoding of \s-1SHA\-1\s0 hash function output.
.SH "RSA ALGORITHM"
.IX Header "RSA ALGORITHM"
The \s-1RSA\s0 algorithm supports encrypt, decrypt, sign, verify and verifyrecover
operations in general. Some padding modes only support some of these 
operations however.
.IP "\-\fBrsa_padding_mode:mode\fR" 4
.IX Item "-rsa_padding_mode:mode"
This sets the \s-1RSA\s0 padding mode. Acceptable values for \fBmode\fR are \fBpkcs1\fR for
PKCS#1 padding, \fBsslv23\fR for SSLv23 padding, \fBnone\fR for no padding, \fBoaep\fR
for \fB\s-1OAEP\s0\fR mode, \fBx931\fR for X9.31 mode and \fBpss\fR for \s-1PSS.\s0
.Sp
In PKCS#1 padding if the message digest is not set then the supplied data is 
signed or verified directly instead of using a \fBDigestInfo\fR structure. If a
digest is set then the a \fBDigestInfo\fR structure is used and its the length
must correspond to the digest type.
.Sp
Note, for \fBpkcs1\fR padding, as a protection against Bleichenbacher attack,
the decryption will not fail in case of padding check failures. Use \fBnone\fR
and manual inspection of the decrypted message to verify if the decrypted
value has correct PKCS#1 v1.5 padding.
.Sp
For \fBoeap\fR mode only encryption and decryption is supported.
.Sp
For \fBx931\fR 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 \s-1ID.\s0 Sign,
verify and verifyrecover are can be performed in this mode.
.Sp
For \fBpss\fR mode only sign and verify are supported and the digest type must be
specified.
.IP "\fBrsa_pss_saltlen:len\fR" 4
.IX Item "rsa_pss_saltlen:len"
For \fBpss\fR 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 \fB\s-1PSS\s0\fR block
structure.
.IP "\fBrsa_pkcs1_implicit_rejection:\fR\fIflag\fR" 4
.IX Item "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.
.SH "DSA ALGORITHM"
.IX Header "DSA ALGORITHM"
The \s-1DSA\s0 algorithm supports signing and verification operations only. Currently
there are no additional options other than \fBdigest\fR. Only the \s-1SHA1\s0
digest can be used and this digest is assumed by default.
.SH "DH ALGORITHM"
.IX Header "DH ALGORITHM"
The \s-1DH\s0 algorithm only supports the derivation operation and no additional
options.
.SH "EC ALGORITHM"
.IX Header "EC ALGORITHM"
The \s-1EC\s0 algorithm supports sign, verify and derive operations. The sign and
verify operations use \s-1ECDSA\s0 and derive uses \s-1ECDH.\s0 Currently there are no
additional options other than \fBdigest\fR. Only the \s-1SHA1\s0 digest can be used and
this digest is assumed by default.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
Sign some data using a private key:
.PP
.Vb 1
\& openssl pkeyutl \-sign \-in file \-inkey key.pem \-out sig
.Ve
.PP
Recover the signed data (e.g. if an \s-1RSA\s0 key is used):
.PP
.Vb 1
\& openssl pkeyutl \-verifyrecover \-in sig \-inkey key.pem
.Ve
.PP
Verify the signature (e.g. a \s-1DSA\s0 key):
.PP
.Vb 1
\& openssl pkeyutl \-verify \-in file \-sigfile sig \-inkey key.pem
.Ve
.PP
Sign data using a message digest value (this is currently only valid for \s-1RSA\s0):
.PP
.Vb 1
\& openssl pkeyutl \-sign \-in file \-inkey key.pem \-out sig \-pkeyopt digest:sha256
.Ve
.PP
Derive a shared secret value:
.PP
.Vb 1
\& openssl pkeyutl \-derive \-inkey key.pem \-peerkey pubkey.pem \-out secret
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fIgenpkey\fR\|(1), \fIpkey\fR\|(1), \fIrsautl\fR\|(1)
\&\fIdgst\fR\|(1), \fIrsa\fR\|(1), \fIgenrsa\fR\|(1)
