Study On Computational Model Of Trust In Peer-to-Peer Distributed File System

With the abroad application of P2P software, the security problem has become the focus of research. The trust mechanism is a very important subject in the field of P2P security. The computational model of trust is the core of trust mechanism, which makes the trust computation and management flexible and adaptive to the network environment. And it also facilitates the change of strategy of trust management by people.This thesis studies the computational models of trust in P2P distributed file system. Based on the study on the normal thoughts for construction of the model and the feathers of P2P distributed file system, a new computational model of trust is designed.In Chapter One the background of the thesis is P2P distributed file system are indicated, which is illustrated by the Gnutella system. Then several current computational models of trust are introduced and analyzed briefly. At last the significance of trust mechanism for the application and development of P2P system are stated.In Chapter Two, the security requirements in P2P system are discussed. Then the role of trust in the field of security and the features of trust in P2P system are studied.In P2P distributed file system, there are not any central severs with complete founctions. That means the construction of trust system depends on non-central or distributed methods. In general, the computation of trust relys on the history of behavior and the recommendations from other peers, and it cannot ensure the correctness of computation. But several errors could be tolerable because of the robustness of P2P system. Furthermore, the normal methods for construction of computational model of trust are analyzed.In Chapter Three, the reasons and feasibility of utilizing Fuzzy theory for the construction of computational model of trust are carefully studied. At last the fundamentals of Fuzzy theory are introduced.In Chapter Four, at first, a general thought for the construction of computational model of trust in this thesis is stated. An idea that the concept of trust would be extended and the factors (represented by parameters) concerning with QoS of file system could be taken into consideration in the computation of trust is presented. According to this, a new computation model of trust is constructed based on the Fuzzy Thoery. And relevant algorithms are given. Because there are many parameters for P2P distributed file system, it is a problem to choice proper parameters for the computation of trust. The thesis attempts to make the right choice.In Chapter Five, the experiment results and analysis for the new model are presented.In the last chapter, Chapter Six, there is a conclusion for this thesis.