A Study Of Critical Nodes Selection And Secure Routing Protocol In Ad Hoc Networks

Ad Hoc network is combined with peer-to-peer technique, wireless communication and mobile computing. It does not rely on any infrastructure communications and can achieve temporary quick, self-organizing communication. The characteristics of Ad Hoc networks, such as dynamically changeful topology, wireless translation and the absence of effective authentic mechanism et al, cause it to suffer from various attacks, such as the typical Do S attacks, fake attack, blackhole attack. By hacking routing information, unauthorized tampering and discarding packets, these attacks can destroy the confidentiality, integrity and non-repudiat ion et al, and cause serious security problems that Ad Hoc networks face.To avoid various attacks in the network, the current secure mechanisms have been developed, such as the intrusion detection, encryption and authentication, secure routing, credibility and trust. For critical nodes selection and secures routing protocol, the trust evaluation mechanism is introduced in this paper. A D-S evidence theory trust evaluation model is established to calculate trust value and evaluate the credibility of node. Once a malicious node is found, it w ill be the isolated from the networks. The trust evaluation mechanism is applied to the critical nodes selection and the establishment of backbone network, clustering and routing selection.The main contributions of the work can be summarized as following:1. Critical nodes selection based on trust evaluat ion in Ad Hoc networks is proposed. The current critical node detection algorithms confine to consider topology partition, but not the reliability of node in communication. Aim ing at selecting the important and trust critical nodes in Ad Hoc networks, the definition of a critical node is given. By using the node contraction method, the importance degree of the node is calculated. Then combined with D-S evidence theory, the trust evaluation model of critic al node is presented, which is used to obtain the objective trust of the node and to judge the credibility of the node. Finally, the critical nodes are selected by considering both the importance degree and the credibility. Simulation experiments show that when those critical nodes are failure, selected by the proposed algorithm, the network performance is decreasing significantly.2. The secure routing protocol based on reliable backbone networks is proposed. Firstly, to select the trust backbone nodes, D-S evidence theory trust evaluat ion mechanism is introduced. The backbone nodes can constitute the backbone link and form the maximal connected subgraph which can overlay network so that two nodes can always select backbone link to communicate. Then backbone nodes are selected as a cluster head node securely to cluster the network and make a trust evaluation to the node who wants to join in the cluster. The ordinary node is allowed into the cluster if it meets the requirements of trust value. The reliable backbone networks are established by cluster head nodes and cluster member nodes. Finally, a secure routing protocol based on reliable backbone networks is designed, in which nodes can communicate in the cluster and between clusters. In the routing process, the behavior of a node is evaluated by sending and responding to a packet. Once a malicious node is found, it will be isolated from the network. Simulat ion exper iments show that secure routing protocol proposed by the paper provides effective protection of network performance under attack.