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Top1. Introduction
The emergence of peer to peer (P2P) network architecture has revolutionaries the computing domain due to the elimination of servers or central control system (client server paradigm) to mediate between end systems. In a client server architecture, a client does not have to be concerned with how the server performs while fulfilling the request and delivering the response. Therefore, all the processes of load balancing, failover system and security are often employed to scale the server implementation. On the other hand, the scalable nature of P2P network makes it an attractive choice for many application domain. In P2P architecture the peers are equally privileged, equipotent participants in the application. They are set to form a peer-to-peer network of nodes with each node plays an independent role in routing and forwarding traffic through the network. A typical example of P2P network include future wireless sensor network (WSN) which are being equipped with the self-organization sensor nodes. Due the autonomous and distributed nature of many WSN, one can argue that the future WSN will be intelligent enough for self-organization and self-decision making capability. With the self-control, anonymous features and the decision making abilities. On the same vein, this development may result to different forms of self-fish behavior and dynamic changes of a node in different form of routing and handling communication tasks between the nodes in the network. Although, many researchers consider the P2P network architecture as a promising solution to the problems and limitations of client server architecture, the security remain one of the challenging problems to be address in emerging P2P WSNs. Therefore, a distributed alternative security solution is needed to tackle different security threats against selfish behaviour of nodes, masquerading behaviour and advanced persistent threat (i.e., using multiple attack vectors to pursue selfish behaviour) which are considered a result of poor self-defensive and poor cooperation between the peers in the network (Han & Sun, 2009) . Unfortunately, the traditional security mechanisms (i.e., cryptography) cannot ensure a high degree of cooperation and self-policing for future WSNs. It is essential to look for an alternative solution to the limitation of cryptography techniques to promote cooperation and easy detection of malicious nodes and malicious behaviour among autonomous WSN-based devices. However, the properties of self-cooperation, self-organization and self-control system of WSN does not come in to existence automatically; it needs to be enforced and managed so that the devices and the protocols of WSN-based devices can be prepared to overcome different problems of variable condition, faulty nodes and any strange or malicious behavior by both inside and outside attacks. The three mechanisms recognized in a decision support research and of relevance to wireless sensor networks are: trust, reputation and cooperation management. This is due to the specific features or mechanism of trust and reputation in dealing with the uncertainty concerning future actions of the participating nodes in the network (Glückler & Armbrüster, 2003).
Our main contributions in this paper are three fold: First, we are introducing the sociological concept of homophily into the wireless sensor network, to propose a new way of interpreting node attributes e.g., node degree as metrics to study the trust and reputation management in WSNs. Second we prove that our proposed structural homophily model is effective to address some common attacks against trust and reputation model (e.g., bad recommendation attack). Last, we reveal some interesting correlations between the proposed homophily model and the critical features of an effective trust and recommendation system in P2P WSN. The rest of the paper is organized as follows: Section 2 reviews related work and the concepts of trust and reputation. Section 3 introduces the structural homophily model and its measures in WSNs, as well as its implications to the network characterises such as network efficiency and redundancy while in section 4 we conducted an extensive simulation studies to explore how the underlying structural homophily impact the overlay trust behaviours. Finally the result analysis and conclusion were presented in section 5.