Crypt::DSA(3) User Contributed Perl Documentation Crypt::DSA(3)NAMECrypt::DSA - DSA Signatures and Key Generation
SYNOPSIS
use Crypt::DSA;
my $dsa = Crypt::DSA->new;
my $key = $dsa->keygen(
Size => 512,
Seed => $seed,
Verbosity => 1
);
my $sig = $dsa->sign(
Message => "foo bar",
Key => $key
);
my $verified = $dsa->verify(
Message => "foo bar",
Signature => $sig,
Key => $key,
);
DESCRIPTIONCrypt::DSA is an implementation of the DSA (Digital Signature Algo-
rithm) signature verification system. The implementation itself is pure
Perl, although the heavy-duty mathematics underneath are provided by
the Math::Pari library.
This package provides DSA signing, signature verification, and key gen-
eration.
USAGE
The Crypt::DSA public interface is similar to that of Crypt::RSA. This
was done intentionally.
Crypt::DSA->new
Constructs a new Crypt::DSA object. At the moment this isn't particu-
larly useful in itself, other than being the object you need to do much
else in the system.
Returns the new object.
$key = $dsa->keygen(%arg)
Generates a new set of DSA keys, including both the public and private
portions of the key.
%arg can contain:
* Size
The size in bits of the p value to generate. The q and g values are
always 160 bits each.
This argument is mandatory.
* Seed
A seed with which q generation will begin. If this seed does not
lead to a suitable prime, it will be discarded, and a new random
seed chosen in its place, until a suitable prime can be found.
This is entirely optional, and if not provided a random seed will
be generated automatically.
* Verbosity
Should be either 0 or 1. A value of 1 will give you a progress
meter during p and q generation--this can be useful, since the
process can be relatively long.
The default is 0.
$signature = $dsa->sign(%arg)
Signs a message (or the digest of a message) using the private portion
of the DSA key and returns the signature.
The return value--the signature--is a Crypt::DSA::Signature object.
%arg can include:
* Digest
A digest to be signed. The digest should be 20 bytes in length or
less.
You must provide either this argument or Message (see below).
* Key
The Crypt::DSA::Key object with which the signature will be gener-
ated. Should contain a private key attribute (priv_key).
This argument is required.
* Message
A plaintext message to be signed. If you provide this argument,
sign will first produce a SHA1 digest of the plaintext, then use
that as the digest to sign. Thus writing
my $sign = $dsa->sign(Message => $message, ... );
is a shorter way of writing
use Digest::SHA1 qw( sha1 );
my $sig = $dsa->sign(Digest => sha1( $message ), ... );
$verified = $dsa->verify(%arg)
Verifies a signature generated with sign. Returns a true value on suc-
cess and false on failure.
%arg can contain:
* Key
Key of the signer of the message; a Crypt::DSA::Key object. The
public portion of the key is used to verify the signature.
This argument is required.
* Signature
The signature itself. Should be in the same format as returned from
sign, a Crypt::DSA::Signature object.
This argument is required.
* Digest
The original signed digest whose length is less than or equal to 20
bytes.
Either this argument or Message (see below) must be present.
* Message
As above in sign, the plaintext message that was signed, a string
of arbitrary length. A SHA1 digest of this message will be created
and used in the verification process.
AUTHOR
Benjamin Trott, ben@sixapart.com
COPYRIGHT
Except where otherwise noted, Crypt::DSA is Copyright 2006 Benjamin
Trott. All rights reserved. Crypt::DSA is free software; you may redis-
tribute it and/or modify it under the same terms as Perl itself.
perl v5.8.8 2004-12-31 Crypt::DSA(3)
