Trust Based Reliable and Secure Routing in Peer-to-Peer Overlay Networks Raja Waseem Anwar Farah Abu Shahla Saqib Ali Arab Open University Arab Open University Sultan Qaboos University Muscat Muscat Muscat KEYWORDS Peer-to-Peer, Trust, Security, Overlay Networks ABSTRACT Increasingly on the Internet, applications are supported by sets of loosely connected machines operating without any form of central coordination and more complex than classical distributed system. Peer-to-peer networking, a disruptive technology for large scale distributed applications, has gained widespread attention due to the successes of peer-to- peer (P2P) content sharing, media streaming, and telephony applications. Peer-to-peer systems are implemented using an abstract overlay network (An overlay network is a computer network which is built on the top of another network) which makes the P2P system independent from the physical network topology. But current overlays network are not secure; even a small segment of malicious nodes can avoid accurate message delivery throughout the overlay network. This problem is particularly serious in open peer-to-peer systems, where many diverse, sovereign parties without previous trust relationships wish to pool their resources. This paper studies types, categories, characteristics and network applications of peer-to-peer (P2P) overlay networks. Also will review and analyze the type of peer-to-peer (P2P) current security attacks and then will present our Hybrid secure routing mechanism in peer- to- peer overlay networks to overcome the security challenges. 1 INTRODUCTION Peer-to-peer (P2P) overlay networks are distributed systems in nature, without any hierarchical organization or centralized control. Peers form self-organizing overlay networks that are overplayed on the Internet Protocol (IP) networks, offering a mix of various features such as robust wide-area routing architecture, efficient search of data items, selection of nearby peers, redundant storage, permanence, hierarchical naming, trust and authentication, anonymity, massive scalability, and fault tolerance [1]. 1.1 Categories of Peer-to-Peer overlay Networks P2P systems can be classified into two types such as, [2].  Unstructured P2P In unstructured P2P system, files can be stored in any peer, that is, the file storage has no certain structure. Unstructured P2P system includes Centralized P2P, pure P2P and Hybrid P2P.  Structured P2P Structured P2P system maintains a link between file contents and IP addresses of the peers using Distributed Hash Table (DHT). Therefore, the whole P2P system holds a certain structure. Normally, structured P2P means DHT-base P2P. 1.2 Characteristics of Peer- to- Peer overlay networks Peer- to- Peer overlay networks are dynamic and distributed systems. It has its own characteristics, which are described below,  Peer-to-peer overlay systems go beyond services offered by client-server systems by having symmetry in roles where a client may also be a server [3].  By having symmetry in roles where a client can also act as a server, they do not have a centralized control or fully responsible storage so that the system can have more robustness for any server node failure and for any congestion or bottleneck problem due to a server [4].  They can also have a scalable storage by utilizing storages of each peer as a part of the whole p2p system’s storage [4].  The peer-to-peer networking mechanism enables all the nodes in the system can look up and consumes the shared content or files stored in other peers [4].  It allows access to its resources by other systems and supports resource sharing, which requires fault- tolerance, self-organization and massive scalability properties [3]. 1.3 Peer- to- Peer overlay networks applications Peer-to-Peer (P2P) overlays have used popularly with the advent of file-sharing applications such as Napster, KaZaa and Bittorrent. In addition to file-sharing and content distribution, P2P networks are also being used for applications such as Voice over IP (VoIP) and television [5].