Research On Trust System Of Wireless Ad Hoc Network

Benefit from absence of fixed infrastructure, wireless ad hoc network is flexible to build up and has good mobility. Hence it is widely applied in the fields of environmental and military and traffic monitoring, rescue, etc. However, these features of wireless ad hoc network increase the difficulty of security defenses. In recent years, advanced research on traditional security technology for wireless ad hoc networks has been made, but it is difficult to provide complete security solutions only depending on traditional security technology. Trust system becomes an essential means in pre-security of wireless ad hoc network because of its important role in security analysis, safety design and guidance to decision-making.Trust system provides security for wireless ad hoc networks, and meanwhile it is a target of malicious attacks. In this dissertation, based on a comprehensive analysis of specific attack behaviors to trust system and trust systems for wireless ad hoc networks with some resilience to specific attacks, a research on resisting specific attack and selfish behavior of nodes is carried out to improve accuracy and stability of trust evaluation in wireless ad hoc network. Trust system is expanded in application for reliable route of wireless ad hoc networks. The main contributions of this dissertation are given as follows.1) A Recommendation Trust Revision Model. Based on Bayesian Decision-Making theory, a novel mechanism for revising the trustworthiness of recommendations of entities is proposed, where deviation of recommendation is characterized by beta distribution. In the model, recommendation trust is revised according to the posteriori distribution of deviation of recommendation and the loss function L. Thereby impact on trust system from the false recommendation caused by liars is reduced. During to limits of ways for getting information in trust system in wireless ad hoc networks, a new scheme of gathering first-hand trust information from non-neighbor nodes based on confirmations is presented. The revision model is fully distributed, no centralized control, and suited to the features of wireless ad hoc network. It enhances the ability of exiting trust systems to resist false recommendation attacks, conflicting behavior attacks and collusion attacks etc., and maintain accuracy and stability of assessment.2) Incentive Strategies for Trust Recommendations. Trust system is completely undefended and vulnerable to selfish refusal to trust recommendation. Meanwhile, trust system itself cannot provide trust evaluations for cooperation of trust-recommended behaviors. To motivate the cooperation, in this dissertation, we propose a repeated probability game model to facilitate the study of the interaction process for trust-recommended behaviors between nodes. Based on the model, we analyze the INFLUENCE of incentive strategies to motivate the trust-recommended behaviors between nodes, as well as the DIFFERENCE of the equilibrium boundary conditions of the four incentives strategies. Both theoretical analysis and simulation results show that, in the high rate of sudden selfish behaviors, GTFT strategy has flexible parameters adjustment mechanism and keeps Efficient Recommendation Ratio at a higher level, motivates the cooperation of trust-recommended behaviors and then helps the trust system to make timely and accurately trust evaluations.3) A Reliable Route Protocol in MANET based on Trust System. First a thorough analysis on the causes of poor reliability of route in MANETs is made and the limits of existing reliable route protocol are reviewed in this dissertation. Then according to DSR protocol, a reliable routing protocol based on local trust system with incentive strategy (TR-DSR) is proposed, which provides specific implementation of GTFT incentive strategy. TR-DSR completely considers and uses the reliability of each node and each link to find reliable routes. Moreover it reduces overhead routing during this process. Extensive simulations are performed to evaluate the proposed scheme. Results indicate that TR-DSR reduces unreliable routes caused by movement of nodes and instability of links and it lessens an impaction on stability of routes due to selfish nodes and congestion compared with existing DSR-EXT, DSR protocol.