ABSTRACT : Peer-to-Peer networks are powerful distributed applications that use the resources of their own users instead of relying on external servers. These days, privacy-preserving plays an important role for users. As a result, security has become an important subject that should be considered as a priority for these networks. There has been a lot of researches to provide security for P2P users. These methods can be categorized as follows: 1- methods based on mixes, 2- innovative tunneling, 3-broadcast encryption, 4- distributed file systems, 5-Friend-to-Friend, and 6- security for structured P2P networks. The purpose of this paper is to review each category and by giving a practical example for each method, show how they work and what their weaknesses are. Studying these methods can provide a good foundation for available security solutions in P2P networks.

Keywords – P2P, Security, Peer-to-Peer, Computer Networks, Structured, Unstructured.