A Game-theoretic Framework for Security-aware Sensor Placement Problem in Networked Control Systems

TL;DR

This paper introduces a game-theoretic approach to optimally place sensors in networked control systems to enhance security against cyber-physical attacks, analyzing equilibrium strategies and their impact on system security.

Contribution

It formulates the sensor placement as a zero-sum game, studies Nash and Stackelberg equilibria, and applies the framework to vehicle platooning, providing new insights into secure sensor deployment.

Findings

Undirected topologies offer higher security than directed ones.

Nash equilibrium exists for tree-structured networks.

Stackelberg equilibrium can be efficiently computed when Nash does not exist.

Abstract

This paper studies the sensor placement problem in a networked control system for improving its security against cyber-physical attacks. The problem is formulated as a zero-sum game between an attacker and a detector. The attacker's decision is to select $f$ nodes of the network to attack whereas the detector's decision is to place $f$ sensors to detect the presence of the attack signals. In our formulation, the attacker minimizes its visibility, defined as the system $L_2$ gain from the attack signals to the deployed sensors' outputs, and the detector maximizes the visibility of the attack signals. The equilibrium strategy of the game determines the optimal locations of the sensors. The existence of Nash equilibrium for the attacker-detector game is studied when the underlying connectivity graph is a directed or an undirected tree. When the game does not admit a Nash equilibrium, it is shown that the Stackelberg equilibrium of the game, with the detector as the game leader, can be computed efficiently. Finally, the attacker-detector game is studied in a cooperative adaptive cruise control algorithm for vehicle platooning problem. The existence of Nash equilibrium is investigated for both directed and undirected platoons and the effect of the position of the reference vehicle on the game value is studied. Our results show that, under the optimal sensor placement strategy, an undirected topology provides a higher security level for a networked control system compared with its corresponding directed topology.