Active eavesdropping in fast fading channels: A Block-Markov Wyner secrecy encoding scheme

This paper studies the problem of active eavesdropping in fast fading channels. The active eavesdropper (Eve-A) is a more powerful adversary than the classical eavesdropper. It can choose between two functional modes: eavesdropping (Ex mode), and jamming (Jx mode) - Eve-A cannot function in full duplex mode. We consider the most conservative scenario, when the Eve-A can choose her strategy based on the legitimate transmitter-receiver pair's strategy - and thus the transmitter and legitimate receiver have to plan for the worst. We introduce a novel encoding scheme, based on very limited and unprotected feedback - the Block-Markov Wyner (BMW) encoding scheme - which outperforms any schemes currently available.