Abstract
The success of a trust management framework acting as a line of defense against various attacks upon Mobile Ad hoc Network is based upon its robustness to various attacks which target its integrity. The current work focuses upon the design of a trust update module for an uncertainty reasoning based trust management framework proposed in our earlier works to provide protection from malicious packet droppers. An on-off attack pattern may be launched by malicious packet droppers which involves periodic good behaviors so as to evade detection and avoid trust degradation. Hence the current paper presents the design of a trust update module which aims to achieve robustness against such on-off malicious packet droppers by performing two forms of trust updates. The former trust updates occur at the end of each session by considering the behavioral consistency over a sequence of sessions and the latter trust updates occur periodically at fixed intervals of time by considering the behavioral consistency of the current session with respect to the behaviors exhibited over all the past sessions. The accuracy of trust evaluation is proved by checking that the overall trust estimate very closely reflects the true nature of the node. The robustness of the scheme and the accuracy of trust computation in the presence of on-off malicious packet droppers are demonstrated through simulation results.