Definitions of PSYC
PSYC is, as benchmarks show, the fastest yet extensible text-based protocol we are aware of, providing a messaging infrastructure for human conversation and social exchange of possibly binary data.
It has learned from protocols such as IRC and XMPP and chose an approach that should scale globally by generalizing the multicast concept beyond programmable chatrooms to presence awareness, event notification, news- and friendcasting. In commercial settings PSYC is also being used for telephony and audio/video.
PSYC provides trust metrics for a distributed social graph and publish/subscribe data. In combination with pseudonymous routing technology it turns into secushare, a platform for distributed social networking and applications that provide cryptographic authentication for the people in it but protect all communications and metadata (the information who is talking to whom) from external observers.
See also the PSYC document and the http://www.psyc.eu website.