The Two-Way Wiretap Channel: Achievable Regions and Experimental Results

TL;DR

This paper explores the two-way wiretap channel, proposing new achievable secrecy rate regions for full-duplex and half-duplex scenarios, and demonstrates practical benefits through experimental results using sensor boards.

Contribution

It introduces novel achievable secrecy rate regions for two-way wiretap channels and develops an experimental testbed to validate the concepts.

Findings

New secrecy rate regions are larger than existing ones for certain channels.

Randomized scheduling significantly improves secrecy sum-rate in half-duplex systems.

Experimental results show effective use of power and scheduling randomization to confuse eavesdroppers.

Abstract

This work considers the two-way wiretap channel in which two legitimate users, Alice and Bob, wish to exchange messages securely in the presence of a passive eavesdropper Eve. In the full-duplex scenario, where each node can transmit and receive simultaneously, we obtain new achievable secrecy rate regions based on the idea of allowing the two users to jointly optimize their channel prefixing distributions and binning codebooks in addition to key sharing. The new regions are shown to be strictly larger than the known ones for a wide class of discrete memoryless and Gaussian channels. In the half-duplex case, where a user can only transmit or receive on any given degree of freedom, we introduce the idea of randomized scheduling and establish the significant gain it offers in terms of the achievable secrecy sum-rate. We further develop an experimental setup based on a IEEE 802.15.4-enabled sensor boards, and use this testbed to show that one can exploit the two-way nature of the communication, via appropriately randomizing the transmit power levels and transmission schedule, to introduce significant ambiguity at a noiseless Eve.