A fundamental problem of Peer-to-Peer file sharing system is how to protect the privacy and anonymity of nodes while providing efficient data access service.We presented a Multicast-based Peer-to-Peer file anonymous retrieval protocol called Mapper.By the combination of IP multicast technology and Multi-proxy forwarding technology

Mapper satisfies the requirements of mutual anonymity during the file access process.The protocol also integrates group member selection with cache position selection via MRFC (Most Requested Frequency Caching) algorithm

thus file distribution can be adjusted adaptively with respect to dynamic usage patterns and multicast overhead can be controlled.The experimental results show that Mapper can alleviate network traffic

reduce access delay efficiently

and has the merits of scalability

reliability and adaptability.