[B<-sigfile file>]
[B<-inkey file>]
[B<-keyform PEM|DER>]
+[B<-passin arg>]
[B<-peerkey file>]
[B<-peerform PEM|DER>]
[B<-pubin>]
[B<-pkeyopt opt:value>]
[B<-hexdump>]
[B<-asn1parse>]
+[B<-engine id>]
=head1 DESCRIPTION
=item B<-keyform PEM|DER>
-the key format PEM or DER.
+the key format PEM, DER or ENGINE.
+
+=item B<-passin arg>
+
+the input key password source. For more information about the format of B<arg>
+see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
+
=item B<-peerkey file>
=item B<-peerform PEM|DER>
-the peer key format PEM or DER.
+the peer key format PEM, DER or ENGINE.
+
+=item B<-engine id>
+
+specifying an engine (by its unique B<id> string) will cause B<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.
+
=item B<-pubin>
the input is a certificate containing a public key.
+=item B<-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.
+
=item B<-sign>
sign the input data and output the signed result. This requires
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 B<digest:alg> option
+which specifies the digest in use for sign, verify and verifyrecover operations.
+The value B<alg> should represent a digest name as used in the
+EVP_get_digestbyname() function for example B<sha1>.
+This value is used only for sanity-checking the lengths of data passed in to
+the B<pkeyutl> and for creating the structures that make up the signature
+(e.g. B<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 B<sha1> the input should be 20 bytes
+long binary encoding of SHA-1 hash function output.
+
=head1 RSA ALGORITHM
-The RSA algorithm supports encrypt, decrypt, sign, verify and verifyrecover
-operations in general. Some padding modes only support some of these
-operations however.
+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
+B<pkeyopt> values are supported:
+
+=over 4
+
+=item B<rsa_padding_mode:mode>
+
+This sets the RSA padding mode. Acceptable values for B<mode> are B<pkcs1> for
+PKCS#1 padding, B<sslv23> for SSLv23 padding, B<none> for no padding, B<oaep>
+for B<OAEP> mode, B<x931> for X9.31 mode and B<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 B<DigestInfo> structure. If a
+digest is set then the a B<DigestInfo> structure is used and its the length
+must correspond to the digest type.
+
+For B<oaep> mode only encryption and decryption is supported.
-[NB: more to be added later]
+For B<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 B<pss> mode only sign and verify are supported and the digest type must be
+specified.
+
+=item B<rsa_pss_saltlen:len>
+
+For B<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 B<PSS> block
+structure.
+
+=back
+
+=head1 DSA ALGORITHM
+
+The DSA algorithm supports signing and verification operations only. Currently
+there are no additional options other than B<digest>. Only the SHA1
+digest can be used and this digest is assumed by default.
+
+=head1 DH ALGORITHM
+
+The DH algorithm only supports the derivation operation and no additional
+options.
+
+=head1 EC ALGORITHM
+
+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 B<digest>. Only the SHA1 digest can be used and
+this digest is assumed by default.
=head1 EXAMPLES
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
+
=head1 SEE ALSO
-L<genpkey(1)|genpkey(1)>, L<pkey(1)|pkey(1)>, L<rsautl(1)|rsautl(1)>
-L<dgst(1)|dgst(1)>, L<rsa(1)|rsa(1)>, L<genrsa(1)|genrsa(1)>
+L<genpkey(1)>, L<pkey(1)>, L<rsautl(1)>
+L<dgst(1)>, L<rsa(1)>, L<genrsa(1)>
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