Enhancing Secrecy Rates in a wiretap channel

TL;DR

This paper introduces a coding scheme that enhances secrecy rates in wiretap channels by using old messages as keys, achieving near-capacity security even under fading conditions and limited eavesdropper channel information.

Contribution

It proposes a novel coding scheme leveraging old messages as keys to improve secrecy rates and demonstrates its effectiveness in fading channels with various levels of channel state information.

Findings

Achieves near-Shannon capacity in fading wiretap channels with full CSI.

Ensures strong secrecy for multiple messages using the proposed scheme.

Effective even when only the distribution of the eavesdropper's channel is known.

Abstract

Reliable communication imposes an upper limit on the achievable rate, namely the Shannon capacity. Wyner's wiretap coding, which ensures a security constraint also, in addition to reliability, results in decrease of the achievable rate. To mitigate the loss in the secrecy rate, we propose a coding scheme where we use sufficiently old messages as key and for this scheme prove that multiple messages are secure with respect to (w.r.t.) all the information possessed by the eavesdropper. We also show that we can achieve security in the strong sense. Next we consider a fading wiretap channel with full channel state information of the eavesdropper's channel and use our coding/decoding scheme to achieve secrecy capacity close to the Shannon capacity of the main channel (in the ergodic sense). Finally we also consider the case where the transmitter does not have the instantaneous information of the channel state of the eavesdropper, but only its distribution.