The Research Of Trust Evaluation In Mobile Ad Hoc Networks

Mobile ad hoc network consists of a team of wireless devices which do not rely on any fixed infrastructure, forming temporary multi-hop wireless network independently. Nodes have limited resources, little memory, poor computing power, and equal status. All network functions are completed by nodes. MANET has such features as dynamic topology, no center, multi-hop routing, and self-organizing, making it promising. However, these features make MANET more vulnerable to attacks compared to traditional networks.If the ad hoc network lacks the security mechanism, the attacker can not only steal data, but also can tamper with the contents of data transmitted between nodes, which destroy data availability and integrity. The limitation of nodes resource causes that network is more vulnerable to resource consumption attacks. The attacker constantly attacks some nodes in the network, and consumes resources, so that these nodes can’t provide normal services. Therefore the security and stability of the entire network are affected, and the network may not run properly.As a relatively flexible security mechanism, trust evaluation provides security for the network through establishing a trust relationship between nodes. Currently, the trust evaluation has become a hot topic in the field of network security. Because of the special characteristics of mobile ad hoc networks and the uncertainty of trust, establishing trust evaluation model with high accuracy and low complexity is still a subject that we have to concern.In this paper, trust evaluation is studied, and the trust model of plane and clustering ad hoc network is also discussed in depth. The main work of the paper is as follows:Firstly, in the MANETs of clustering structure, a trust model based on multi-role is proposed. Most existing models use single criterion for head node selection, and have difficulties with assigning and updating trust value of the different roles. This paper proposes a new multi-role trust evaluation model. The node has four roles: cluster head, cluster members, gateways and agent. Thus, a new way comes out to compute the trust of cluster head by using trust value, mobility and correlation degree of node as selecting criteria of cluster heads, gateways and agent. In this paper, the multi-role model enriches the roles of node. The different roles are decided according to different selection criteria, and their trust value is allocated reasonably. The experiment shows the model can effectively detect malicious nodes in the network to ensure the routing reliability, and improve the network security.Secondly, in the MANETs of plane structure, a multi-dimensional trust evaluation model based on AHP is proposed. Because of the various influence factors of trust, constrained energy of MANETs nodes and calculation difficulty of recommended trust, direct trust, recommended trust, incentive function and risk function are introduced to evaluate trust value. Nodes that have enough residual energy get the opportunity to participate in the network activities, so direct trust are divided into behavior trust and energy trust. The semi-ring theory is used to define recommended trust, and to solve the difficult problem of transferring recommended trust. Finally, we implement the proposed protocol with NS2, which has verified its correctness and effectiveness.