Achieving both positive secrecy rates of the users in two-way wiretap channel by individual secrecy

TL;DR

This paper investigates the individual secrecy capacity of two-way wiretap channels, deriving new achievable regions and bounds, and demonstrating that individual secrecy can outperform joint secrecy in certain scenarios.

Contribution

It introduces the first achievable secrecy rate region for two-way wiretap channels with individual secrecy and establishes secrecy capacity regions for specific channel models.

Findings

The achievable secrecy rate region with individual secrecy is larger than that with joint secrecy in deterministic channels.

Secrecy capacity regions are explicitly derived for XOR and degraded Gaussian two-way wiretap channels.

The secure sum-rate under individual secrecy exceeds that under joint secrecy in degraded Gaussian channels.

Abstract

In this paper, the individual secrecy of two-way wiretap channel is investigated, where two legitimate users' messages are separately guaranteed secure against an external eavesdropper. For one thing, in some communication scenarios, the joint secrecy is impossible to achieve both positive secrecy rates of two users. For another, the individual secrecy satisfies the secrecy demand of many practical communication systems. Thus, firstly, an achievable secrecy rate region is derived for the general two-way wiretap channel with individual secrecy. In a deterministic channel, the region with individual secrecy is shown to be larger than that with joint secrecy.Secondly, outer bounds on the secrecy capacity region are obtained for the general two-way wiretap channel and for two classes of special two-way wiretap channels.The gap between inner and outer bounds on the secrecy capacity region is explored via the binary input two-way wiretap channels and the degraded Gaussian two-way wiretap. Most notably, the secrecy capacity regions are established for the XOR channel and the degraded Gaussian two-way wiretap channel.Furthermore, the secure sum-rate of the degraded Gaussian two-way wiretap channel under the individual secrecy constraint is demonstrated to be strictly larger than that under the joint secrecy constraint.