A Game-Theoretic Approach to Covert Communications

TL;DR

This paper models covert communication as a game between transmitter and warden, deriving Nash equilibria to optimize coding rates and demonstrate improvements with power variation and jamming strategies.

Contribution

It introduces a novel game-theoretic framework for finite blocklength covert communications, including strategies with power variation and jamming, and provides efficient equilibrium computation methods.

Findings

Nash equilibria can be efficiently computed using linear programming.

Power variation strategies significantly improve coding rates for less covert requirements.

Adding a jammer further enhances covert communication performance.

Abstract

This paper considers a game-theoretic formulation of the covert communications problem with finite blocklength, where the transmitter (Alice) can randomly vary her transmit power in different blocks, while the warden (Willie) can randomly vary his detection threshold in different blocks. In this two player game, the payoff for Alice is a combination of the coding rate to the receiver (Bob) and the detection error probability at Willie, while the payoff for Willie is the negative of his detection error probability. Nash equilibrium solutions to the game are obtained, and shown to be efficiently computable using linear programming. For less covert requirements, our game-theoretic approach can achieve significantly higher coding rates than uniformly distributed transmit powers. We then consider the situation with an additional jammer, where Alice and the jammer can both vary their powers. We pose a two player game where Alice and the jammer jointly comprise one player, with Willie the other player. The use of a jammer is shown in numerical simulations to lead to further significant performance improvements.