Research On Dynamic Trust Management For Large Scale Distributed Environment

With the development of Internet technology, large-scale distributed computing environ-ments such as P2P computing, grid computing, Ad Hoc networks, social networks have beenwidely used. The new application models in such computing environment typically be com-posed by multiple heterogeneous systems or software services. Now, such models moving fromthe closed, facing familiar user groups, relatively static form, to open for public users, dynamiccollaboration paradigm shift. These features give the great complexity and dynamic to thesesystems. It is impossible to "Control" this systems, i.e. that is difficult to use traditional cen-tral control mechanisms to manage the security of such systems. Meanwhile, P2P file sharingsystem, large e-commerce systems, social networking sites as a representative of these new ap-plication models also brings information overload, the "selfish" node and other new issues.Human society also has the above characteristics, and maybe more significant."Trust"is one of the cornerstones of human society. In the social sciences, business and many otherareas, especially in people’s daily life, trust is happening in the moment of action. Therefore,by drawing sociology, psychology and other fields of research about trust, trust management iswidely researched in computer science in recent years. These researches want to use "trust" tosimplify the complexity of the systems.Thisthesismainlyfocusonthecharacteristicsoflarge-scaledistributedcomputingenviron-ment. We has proposed suitable dynamic trust management mechanisms for this environment,and explored the possible ways to address the new issues such as the information overload and"selfish" node by using trust management mechanisms. The main contents and novelties areillustrated as follows:1)The current trust management mechanisms, usually using mathematical, artificial intelli-gence and other aspects of the theory and methods to describe the formal relations of trust undercertain circumstances, in order to achieve trust evaluation in these environment. We analyzedthe characteristics of dynamic trust in large-scale distributed computing environment by draw-ing sociology, psychology and other fields of research about trust, summarized the progressof the research progress of trust in computer science, discussed the characteristics of dynamictrust management mechanism in large-scale distributed computing environment. On this ba- sis, we proposed a reputation-based distributed dynamic trust management mechanism. Thismechanism, as a "soft security" mechanism, can be a useful supplement to the traditional secu-rity mechanism. This mechanism can collaborate with the traditional security mechanisms toachieve security in large-scale distributed computing environment.2)Most of the existing trust management mechanisms are using fixed formulas and prede-fined parameters to describe the trust relationship. These mechanisms always have two prob-lems: one is the fixed formulas and predefined parameters can not adopt the dynamic envi-ronment; the other is the fixed formulas and predefined parameters can not describe the fuzzyrelationship between different attributes of trust. We designed a dynamic evaluation model formulti-attributes trust relationship. This model achieves the learning ability by using evolution-ary computing. With autonomous learning, the model can improve it’s evaluation performanceof its own. Therefore, this model can adopt the the dynamic environment and describe the fuzzyrelationship between different attributes of trust.3)Addressing the information overload is a crucial issue for today’s large-scale e-businessapplications. Collaborative filtering is a hot-spot in recent research of personalized recommen-dation systems. We argued the relationship between collaborative filtering and trust manage-ment. Byunifyingthetrust,theevaluation,andtherecommendation,wedesignedapersonalizedrecommendation systems based on reputation. User can predict his rating on the unknown re-sources by the reputation of the other users and the recommendation of the others. By using thetrust management mechanism, the system can address the problems caused by sparse rating andunreliable rating. Therefore, the system can improve the accuracy of the prediction.4)The evolution of cooperation between selfish individuals is a fascinating topic that hasattracted scientists in different fields. This question is also beginning to arise in computer sys-tems. The P2P systems are characterized by heterogeneous components that interact to achievethe public goals. Thus, the free-riding problem will caused by selfish individuals in these sys-tems. We argued that the trust information is an important factor in the rise of cooperativebehaviors in the evolution of a group of selfish individuals. Therefore, we explored the cooper-ation stimulation mechanisms based on trust. This thesis designed an evolutionary game basedon classic prisoners dilemma game. A cooperation stimulation mechanism based on trust hasbeen put in this game. The individuals update their strategies and adjust their relationship with others merely according to the opponents’ trust information. The result of the game illustratedthe effectiveness of our mechanism.