Research Of An Improved Hybrid Trust Model In P2P Networks

A P2P trust model is the key point to solving the security problems of P2P networks. However, there are many weaknesses in existing trust models, such as one-sidedness and inaccuracy in trust value calculation, the ineffective prohibition of cooperation cheating and so on. Therefore, based on the study and reference of the existing P2P trust models, the thesis analyzes the key points in a P2P trust model and proposes an improved hybrid trust model in P2P networks according to above problems.The trust model is a hybrid one that combing direct trust and indirect trust. In direct trust, the thesis utilizes transaction amount, transaction time, transaction evaluation value, etc. from the transaction history records of the peer and its objective peer to compute trust value. In order to restrain pure malicious transactions and vibrating transactions in the networks more effectively, by emphatically analyzing its influencing factors of transaction failure times and penalty factor, the thesis improves the situation of the same penalty by each failure in the general trust models, and makes each penalty aggravated as the failure times increases. In this way, trust value can be reasonably computed.In indirect trust, the trust value is computed by recommended value and recommendation trust value of the recommenders. The peers in the networks store not only the recommended value of recommenders, but also the recommendation trust value of theirs. In order to distinguish recommendation trust value of different recommenders, the thesis refines the recommenders for known peers and unknown peers, so as to remarkably restrain cooperation cheating of recommenders. Then by comparing the recommenders' recommended value with the objective peer's actual trust value, the restored recommendation trust value of the recommenders can be updated to provide reference to their later recommendation. This mechanism can effectively restrain malicious recommendation in a long-term significance.The simulating experiment shows that the proposed model can effectively evaluate the trust value of peers. Through the comparison between the proposed trust model and other traditional trust models, the proposed one has better performance in restraining the malicious attacks and improving the rate of successful transactions in the networks.