Enhancing Secrecy Rate Region for Recent Messages for a Slotted Multiple Access Wiretap Channel to Shannon Capacity Region

TL;DR

This paper introduces a coding scheme for a two-user MAC-WT that uses previous messages as keys, significantly improving secrecy rates and achieving the Shannon capacity region even in fading channels.

Contribution

It proposes a novel coding scheme utilizing past messages as keys to enhance secrecy rates in MAC-WT, approaching the capacity of a non-wiretap MAC.

Findings

Achieves the Shannon capacity region for MAC without wiretapper.

Ensures all recent messages remain secure against eavesdroppers.

Applicable to fading MAC channels in ergodic conditions.

Abstract

Security constraint results in \textit{rate-loss} in wiretap channels. In this paper we propose a coding scheme for two user Multiple Access Channel with Wiretap (MAC-WT), where previous messages are used as a key to enhance the secrecy rates of both the users until we achieve the usual capacity region of a Multiple Access Channel (MAC) without the wiretapper (Shannon capacity region). With this scheme all the messages transmitted in the recent past are secure with respect to all the information of the eavesdropper till now. To achieve this goal we introduce secret key buffers at both the users, as well as at the legitimate receiver (Bob). Finally we consider a fading MAC-WT and show that with this coding/decoding scheme we can achieve the capacity region of a fading MAC (in ergodic sense).