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Delay Tolerant Network (DTN) provides connectivity where there is uncertainty in end-to-end connectivity. In DTN, nodes exchange bu�ered messages upon an encounter. In disaster operations where the telecommunication and power infrastructures are completely broken down or destroyed, DTN can be used to support emergency communication till these infrastructures are restored. Security in DTN remains a major challenge because of its network characteristics such as frequent disruptions, dynamic topology, limited and constrained resources. One of the major threats in DTN is Denial of Service (DoS) attacks. This attack mainly comes from intermediary nodes that drop or fl ood packets in the network which often results in the degradation of the network performance. This thesis proposes strategies for mitigating routing misbehaviour in emergency communications using DTN. This thesis proposes three innovative contributions as follows. A Collaborative Content-aware Trust Management Scheme (CCTMS) is proposed for secure routing optimisation. CCTMS incorporates structural and content similarities into the routing decision process. A trust model is developed based on direct and indirect interactions between nodes using Beta distribution model, which is used to evaluate the forwarding behaviour of encountered nodes. To optimise the routing decision, the recurrence in mobility pattern of the nodes are also exploited to form transitive similarity. The logical properties of the contents generated by the mobile nodes are also exploited to form content similarity. However, since CCTMS still incurs a high overhead and signi�cant delay, a Distributed Trust Management Scheme (DTMS) is proposed. Energy trust is integrated into the direct trust computation model as a trust metric and inter-contact graph is introduced for the computation of transitive similarity. In DTMS, the inter-contact graph is formed by the encounter between two nodes where each vertex represents an encounter between two nodes. The novelty of the inter-contact graph is the capturing of the latency distributions for each encounter between nodes. Finally, the limitation in resource constrained networks is taken into consideration and energy is identi�ed as a vital resource to ensure availability of communication in a resource constrained networks. An Energy-e�cient Semi-distributed Trust Management Scheme (ESTMS) is proposed for resource constrained emergency response networks. ESTMS assumes that trusted entities are available at each emergency response centre and are responsible for computing and �ltering recommendations. Although ESTMS increases the delivery ratio and significantly reduces the overhead ratio, it has a higher delay when compared to CCTMS and DTMS. Extensive simulations and validations show that the proposed schemes outperform existing routing and trust management protocols in the presence of malicious nodes and are resilient to trust related attacks. |
