Security and Trust in Mobile Ad-Hoc Networks

Abstract

Distributed ad-hoc networks have become ubiquitous in the current technological framework. Such networks have widespread applications in commercial, civil and military domains. Systems utilizing these networks are deployed in scenarios influencing critical aspects of human lives, e.g.: vehicular networks for road safety, infrastructure monitoring for smart grid or wildlife, and healthcare systems.

The pervasive nature of such systems has made them a valuable target for adversarial action. The risk is compounded by the fact that typically the networks are composed of low power, unattended devices with limited protection and processing capabilities. Usage of cryptographic primitives can prove to be a significant overhead in these scenarios. Further, behavioral aspects of participants, that are critical for distributed system operation, are not effectively addressed by cryptography.

In this dissertation, we explore the direction of using notions of trust and privacy to address security in these networks. In the first part of the dissertation, we consider the problems of generation, distribution and utilization of trust metrics. We adopt a cross-layer and component based view of the network protocols. We propose schemes operating at the physical layer of the communication stack, to generate trust metrics. We demonstrate that these schemes reliably detect relay adversaries in networks, and can be an effective measure of trust for the neighborhood discovery component. We propose techniques to combine trust from different detectors across multiple layers into a singular trust metric.

Further, we illustrate via simulations, the advantages and disadvantages of existing techniques for propagation of local trust metrics throughout the network. We propose modifications to increase the robustness of the semiring based framework for trust propagation. Finally, we consider utilization of trust metrics to increase resilience of network protocols. We propose a distributed trust based framework, to secure routing protocols such as AODV, DSR. We highlight utility of our framework by using the proposed point-to-point link trust metrics.

In the second part of the dissertation, we focus on the role of privacy in ad-hoc networks. We demonstrate that for three broad categories of systems; distributed state estimation, distributed consensus and distributed monitoring systems, privacy of context can reduce cryptographic requirements (such as the need for encryption). In fact, efficient methods to preserve privacy can significantly reduce the energy footprint of the overall security component. We define a privacy framework applicable to these scenarios, where the network can be partitioned into a hierarchical structure of critical and non-critical components. We utilize a physical layer watermarking scheme to ensure privacy guarantees in our framework. Further, for systems that lack a natural hierarchical structure, such as information fusion systems, we define an efficient framework to define a hierarchy (network partition), without leaking the structure to the adversary.