Identifying Collusion Attack in P2P Trust and Reputation Systems

Internet became today a medium of sharing large amount of data among different nodes situated anywhere in the world. Due to its fairly open nature Peer to Peer applications gain-ing popularity in sharing of large data rather then conventional client-server systems. Many P2P applications has been designed for the purpose of content distribution over Internet and most of them are based on decentralized Peer to peer architecture. Although absence of a central server, peers can communicate directly but lacks of central administration makes P2P network vulnerable to various kind of attacks. Authenticity of data become a major challenge in decentralized P2P content distribution applications since peers are unknown to each other within a network. To ensure the data authenticity, several schemes had been proposed by trust and reputation systems in recent past few years. In literature, we have covered the desirable characteristics of trust and reputation systems. Trust and reputation system play a vital role in defining the trustworthiness of a peer before making transaction. On the basis of trust value requester can able to skip malicious identities. However due to malicious behaviour of peers, they themselves are vulnerable to various kinds of attacks. The paper reviews existing collusion attacks.