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.\" ========================================================================
.\"
.IX Title "Crypt::RSA::SS::PSS 3"
.TH Crypt::RSA::SS::PSS 3 "2009-06-06" "perl v5.8.8" "User Contributed Perl Documentation"
.SH "NAME"
Crypt::RSA::SS::PSS \- Probabilistic Signature Scheme based on RSA. 
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&    my $pss = new Crypt::RSA::SS::PSS;
.Ve
.PP
.Vb 4
\&    my $signature = $pss->sign (
\&                        Message => $message,
\&                        Key     => $private, 
\&                    ) || die $pss->errstr;
.Ve
.PP
.Vb 5
\&    my $verify    = $pss->verify (
\&                        Message   => $message, 
\&                        Key       => $key, 
\&                        Signature => $signature, 
\&                    ) || die $pss->errstr;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\s-1PSS\s0 (Probabilistic Signature Scheme) is a provably secure method of
creating digital signatures with \s-1RSA\s0. \*(L"Provable\*(R" means that the
difficulty of forging signatures can be directly related to inverting
the \s-1RSA\s0 function. \*(L"Probabilistic\*(R" alludes to the randomly generated salt
value included in the signature to enhance security. For more details
on \s-1PSS\s0, see [4] & [13].
.SH "METHODS"
.IX Header "METHODS"
.Sh "\fB\fP\f(BInew()\fP\fB\fP"
.IX Subsection "new()"
Constructor. 
.Sh "\fB\fP\f(BIversion()\fP\fB\fP"
.IX Subsection "version()"
Returns the version number of the module. 
.Sh "\fB\fP\f(BIsign()\fP\fB\fP"
.IX Subsection "sign()"
Computes a \s-1PSS\s0 signature on a message with the private key of the signer.
In scalar context, \fIsign()\fR returns the computed signature. In array
context, it returns the signature and the random salt. The signature can
verified with \fIverify()\fR or \fIverify_with_salt()\fR. \fIsign()\fR takes a hash argument
with the following mandatory keys:
.IP "\fBMessage\fR" 4
.IX Item "Message"
Message to be signed, a string of arbitrary length.  
.IP "\fBKey\fR" 4
.IX Item "Key"
Private key of the signer, a Crypt::RSA::Key::Private object.
.Sh "\fB\fP\f(BIverify()\fP\fB\fP"
.IX Subsection "verify()"
Verifies a signature generated with \fIsign()\fR. The salt is recovered from the
signature and need not be passed. Returns a true value on success and
false on failure. \f(CW$self\fR\->errstr is set to \*(L"Invalid signature.\*(R" or
appropriate error on failure. \fIverify()\fR takes a hash argument with the
following mandatory keys:
.IP "\fBKey\fR" 4
.IX Item "Key"
Public key of the signer, a Crypt::RSA::Key::Public object. 
.IP "\fBMessage\fR" 4
.IX Item "Message"
The original signed message, a string of arbitrary length. 
.IP "\fBSignature\fR" 4
.IX Item "Signature"
Signature computed with \fIsign()\fR, a string. 
.IP "\fBVersion\fR" 4
.IX Item "Version"
Version of the module that was used for creating the Signature. This is an
optional argument. When present, \fIverify()\fR will ensure before proceeding
that the installed version of the module can successfully verify the
Signature.
.Sh "\fB\fP\f(BIverify_with_salt()\fP\fB\fP"
.IX Subsection "verify_with_salt()"
Verifies a signature given the salt. Takes the same arguments as \fIverify()\fR
in addition to \fBSalt\fR, which is a 20\-byte string returned by \fIsign()\fR in
array context.
.SH "ERROR HANDLING"
.IX Header "ERROR HANDLING"
See \s-1ERROR\s0 \s-1HANDLING\s0 in \fICrypt::RSA\fR\|(3) manpage.
.SH "BIBLIOGRAPHY"
.IX Header "BIBLIOGRAPHY"
See \s-1BIBLIOGRAPHY\s0 in \fICrypt::RSA\fR\|(3) manpage.
.SH "AUTHOR"
.IX Header "AUTHOR"
Vipul Ved Prakash, <mail@vipul.net>
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fICrypt::RSA\fR\|(3), \fICrypt::RSA::Primitives\fR\|(3), \fICrypt::RSA::Keys\fR\|(3),
\&\fICrypt::RSA::EME::OAEP\fR\|(3)