Study Of Trust Management For Resource Sharing On Wireless Ad Hoc Networks

At the present time, the application range of wireless Ad Hoc networks has spread from military areas and exploration areas to areas of daily life that brought people lots of convenience. However, security is the barrier which blocks the further development of wireless Ad Hoc networks all the time. Due to the leak of security infrastructure and the mobility of nodes, wireless Ad Hoc networks should face threats and attacks more easily comparing to the wired networks. Existing security technologies which do not apply to open peer-to-peer networks without third party mainly implement encryption algorithms through security infrastructure to achieve secure communication of messages. Due to The introduction of trust management model, wireless Ad Hoc networks can forecast and control behavior of nodes to strengthen networks security.Firstly, this dissertation analyzes the features of wireless Ad Hoc networks and the security threats that wireless Ad Hoc networks faced, and points out the importance of the introduction of trust model. Then we introduce the conception and features of trust management, and discuss various trust models. We find that policy-based trust models should not suit to wireless Ad Hoc networks and reputation-based trust models can resolve the security issues of wireless Ad Hoc networks. Background of the thesis is file-sharing application of wireless Ad Hoc networks. A node should evaluate the trust value of other nodes before downloading files, and choose node which has high trust value to download files. SoTrust which is a new trust model was proposed in this paper. In SoTrust model, nodes should calculate direct trust value and indirect trust value respectively, and then make combination of the two trust values to integrated trust value. When calculate direct trust value, SoTrust introduces weights assigned to files. It is effective to prevent malicious behaviors implemented through the accumulation of reputation. Meanwhile, SoTrust combines integrated trust value and risk value to form final trust value. Due to the introduction of risk element, the model becomes more sensitive to malicious behaviors and more immune to the sudden changes of nodes' behaviors. In order to suit the resources-limited feature of wireless Ad Hoc networks, three parameters are set. Through the three parameters, nodes can save storage space and computing time, and reduce the traffic of communication. Subsequent experiments show that, compared with wireless Ad Hoc networks without trust model, the proposed model can identify malicious nodes effectively and reduce the number of bad transactions notably.Finally, the thesis discusses the ways of implementing P2P applications on wireless Ad Hoc networks. P2P refers to application layer in the protocol stack, while wireless Ad Hoc networks focuses on the network and lower layers. Therefore the key of implementing P2P applications on wireless Ad Hoc networks is how to replace network and lower layers of wired networks with network and lower layers of wireless Ad Hoc networks. This thesis introduces two implementation methods. The one is through integrating P2P protocol and AODV protocol, another one is through designing cross-layer communication channel.