Files are identified by applying a strong hash function to their contents, which gives a distinct "fingerprint" for each file. Bitzi calls the combination of standard hash functions used by its system "Bitprints."
The Bitzi catalog is a project of a company based in San Francisco.
Some peer-to-peer file sharing programs offer an option to look up local files or network search results at the Bitzi website for more (or more trustworthy) information.
Website: http://bitzi.com