Half-Duplex Active Eavesdropping in Fast Fading Channels: A Block-Markov Wyner Secrecy Encoding Scheme

TL;DR

This paper introduces a new Block-Markov Wyner encoding scheme to enhance physical-layer secrecy against a powerful half-duplex active eavesdropper in fast fading channels, outperforming existing methods.

Contribution

The paper proposes a novel encoding scheme that leverages limited feedback to counteract active eavesdropping strategies in fast fading channels.

Findings

BMW scheme outperforms existing secrecy methods

Conventional approaches perform poorly against active eavesdroppers

Limited feedback can significantly improve secrecy performance

Abstract

In this paper we study the problem of half-duplex active eavesdropping in fast fading channels. The active eavesdropper is a more powerful adversary than the classical eavesdropper. It can choose between two functional modes: eavesdropping the transmission between the legitimate parties (Ex mode), and jamming it (Jx mode) -- the active eavesdropper cannot function in full duplex mode. We consider a conservative scenario, when the active eavesdropper can choose its strategy based on the legitimate transmitter-receiver pair's strategy -- and thus the transmitter and legitimate receiver have to plan for the worst. We show that conventional physical-layer secrecy approaches perform poorly (if at all), and we introduce a novel encoding scheme, based on very limited and unsecured feedback -- the Block-Markov Wyner (BMW) encoding scheme -- which outperforms any schemes currently available.