Any peer-to-peer publishing system must provide a mechanism for efficiently locating published documents. For censorship resistant systems, it is particularly important that the lookup mechanism be difficult to disable or abuse.
Li Fan, Pei Cao and Jussara Almeida & Andrei Z. Broder - this new protocol, each proxy keeps a summary of the cache directory of each participating proxy, and checks these summaries for potential hits before sending any queries.