This is a perl implementation of the [Salmon Protocol] for distributed feedback to Atom feeds.
A "lightweight, robust mechanism for digitally signing nearly arbitrary messages, along with a basic public key infrastructure for discovering the signing keys." A perl implementation of the Magic Signatures from the Salmon protocol.
The Magic Signatures spec is still in draft form and can be found at:
http://salmon-protocol.googlecode.com/svn/trunk/draft-panzer-magicsig-00.html