A Trust Management Based Security Mechanism against Collusion Attacks in a MANET Environment

MANETs (Mobile Ad hoc Networks) are self organized networks with mobile and collaborating nodes without any pre-established infrastructure. Because of these characteristics, securing MANETs constitute a hard and challenging task. Consequently, new mechanisms may be of interest to secure such networks. To this end, we have found that trust management can be a support for MANET security. In fact, the reputation concept and the establishment of trustful relation between collaborating nodes can be meaningful to express security aspects in such environment. From there, we proposed in previous works a Mobility-based Clustering Algorithm (MCA) and a Trust management scheme for MCA (TMCA) to secure routing behaviors. MCA organizes nodes into clusters managed by a cluster-head (CH) and TMCA detects malicious routing behavior based on CHs direct observations and exchanged alerts. A delegation based process was also defined on TMCA and was called DTMCA. Although DTMCA meets security objectives, it may unfortunately be faced with various threats from malicious nodes: Several nodes can in fact collude in order to increase or decrease other reputation values to damage the QoS and even the MANET functioning. Our objective in this paper is then to secure DTMCA against collusion attacks. The mechanism proposed here is based on colluding nodes detection through cluster members behavior monitoring and by comparing this behavior with the received reputation value in the alert message. Detected colluder nodes are then discarded from further communication.