NAME Crypt::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, ); DESCRIPTION *Crypt::DSA* is an implementation of the DSA (Digital Signature Algorithm) 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 generation. 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 particularly 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 generated. 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 success 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. TODO Add ability to munge format of keys. For example, read/write keys from/to key files (SSH key files, etc.), and also write them in other formats. SUPPORT Bugs should be reported via the CPAN bug tracker at <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Crypt-DSA> For other issues, contact the author. AUTHOR Benjamin Trott <ben@sixapart.com> COPYRIGHT Except where otherwise noted, Crypt::DSA is Copyright 2006 - 2011 Benjamin Trott. Crypt::DSA is free software; you may redistribute it and/or modify it under the same terms as Perl itself.