Opportunism, Cooperation and Feedback for Wireless Secrecy

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The design of efficient wireless networks presents exciting challenges which are markedly different from their counterparts in wire-line networks. Of particular interest is the perceived vulnerability of wireless networks to security attacks. Ensuring network robustness against various types of security threats is, therefore, one of the important design objectives.This project adopts a new optimistic perspective in which the wireless medium is viewed as a resource instead of a liability. In particular, we identify three principles, namely opportunism, cooperation and feedback by which the wireless channel can be efficiently exploited to counter passive eavesdropping attacks. The first research thrust is dedicated to developing an opportunistic secrecy framework in which the multi-path fading fluctuations are used to create an advantage for the legitimate destination(s) overthe eavesdropper(s). Our investigations seek to characterize the fundamental limits of opportunistic secrecy and develop low complexity protocols capable of leveraging the corresponding performance gain. The second research thrust aims to: 1) develop novel cooperation strategies inspired by the secrecy constraint, 2)derive sharp secrecy capacity results for certain instances of the relay-eavesdropper channel and 3) identify the scaling behavior of cooperative secrecy protocols in large scale hierarchical and ad-hocwireless networks. Finally, the third thrust involves characterizing the fundamental limits of secure communication over closed loop channels and the structure of the corresponding feedback policies inthe context of memoryless, fading and multi-user channels.