The Gaussian Wiretap Channel with a Helping Interferer

TL;DR

This paper investigates how a helping interferer can enhance secure communication over a Gaussian wiretap channel by exploiting wireless superposition, providing bounds on secrecy capacity and analyzing their tightness.

Contribution

It introduces a new model of a Gaussian wiretap channel with a helping interferer and derives achievable secrecy rates and upper bounds for this scenario.

Findings

Upper bound on secrecy capacity close to achievable rate in weak interference

Helping interferer improves secrecy in Gaussian channels

Bounds are tight under symmetric and some asymmetric conditions

Abstract

Due to the broadcast nature of the wireless medium, wireless communication is susceptible to adversarial eavesdropping. This paper describes how eavesdropping can potentially be defeated by exploiting the superposition nature of the wireless medium. A Gaussian wire-tap channel with a helping interferer (WTC-HI) is considered in which a transmitter sends confidential messages to its intended receiver in the presence of a passive eavesdropper and with the help of an interferer. The interferer, which does not know the confidential message assists the confidential message transmission by sending a signal that is independent of the transmitted message. An achievable secrecy rate and a Sato-type upper bound on the secrecy capacity are given for the Gaussian WTC-HI. Through numerical analysis, it is found that the upper bound is close to the achievable secrecy rate when the interference is weak for symmetric interference channels, and under more general conditions for asymmetric Gaussian interference channels.