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

摘要

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