package Object::Signature; # git description: 5b580b0

use strict;
use warnings;

our $VERSION = '1.08';

use Storable    2.11 ();
use Digest::MD5 2.00 ();

sub signature {
	local $Storable::canonical = 1;




=head1 NAME

Object::Signature - Generate cryptographic signatures for objects


  # In your module
  package My::Module
  use base 'Object::Signature';
  # In outside code
  my $Object = My::Module->new;  
  print "Object Signature: " . $Object->signature;


L<Object::Signature> is an abstract base class that you can inherit from in
order to allow your objects to generate unique cryptographic signatures.

The method used to generate the signature is based on L<Storable> and
L<Digest::MD5>. The object is fed to C<Storable::nfreeze> to get a string,
which is then passed to L<Digest::MD5::md5_hex> to get a unique 32
character hexadecimal signature.

=head1 METHODS

=head2 signature

The C<signature> method is the only method added to your class, and will
generate a unique 32 hexadecimal signature for any object it is called on.

=head1 SUPPORT

All bugs should be filed via the bug tracker at


For other issues, or commercial enhancement or support, contact the author.

=head1 TO DO

=head2 Incremental Generation

Currently has to generate the entire Storable string before digesting
it. Would be nice if there was a way to incrementally Storablise and Digest
in one pass so that it becomes much more memory efficient for large objects.

=head2 Strengthen the Digest Algorithm

Once the current (as of 2005) hashing controversy settles down, consider
selecting a newer and more powerful hashing algorithm to replace MD5. Or
offer alternatives depending on how important the security situation is,
as MD5 is B<very> fast (90 meg a second) and many more-secure ones are a
lot slower (more than 10 times slower in some cases).

On our side is the fact we use Storable. It should be B<much> harder to create
collisions when you don't control the string, only the structure B<before>
it goes through Storable.

=head1 AUTHOR

Adam Kennedy E<lt>adamk@cpan.orgE<gt>

=head1 SEE ALSO

L<Object::Signature::File>, L<>


Copyright 2004 - 2011 Adam Kennedy.

This program is free software; you can redistribute
it and/or modify it under the same terms as Perl itself.

The full text of the license can be found in the
LICENSE file included with this module.