An On-line Design of Physical Watermarks

TL;DR

This paper introduces an online method for designing physical watermarks in control systems to detect replay attacks, balancing control performance and attack detection effectiveness, with solutions for systems with unknown parameters.

Contribution

It proposes an optimal, adaptive watermark design scheme for replay attack detection in control systems, including systems with unknown parameters.

Findings

The watermarking scheme effectively detects replay attacks.

Optimal trade-off between control performance and attack detection achieved.

Numerical examples demonstrate the strategy's effectiveness.

Abstract

This paper considers the problem to design physical watermark signals to protect a control system against replay attacks. We first define the replay attack model, where an adversary replays the previous sensory data in order to fool the system. The physical watermarking scheme, which leverages a random control input as a watermark, to detect the replay attack is introduced. The optimal watermark signal design problem is then proposed as an optimization problem, which achieves the optimal trade-off between the control performance and attack detection performance. For the system with unknown parameters, we provide a procedure to asymptotically derive the optimal watermarking signal. Numerical examples are provided to illustrate the effectiveness of the proposed strategy.