An On-line Design of Physical Watermarks
For control system security, this work provides a principled approach to watermark design, but it is incremental as it builds on existing watermarking concepts.
This paper addresses replay attacks on control systems by designing optimal physical watermark signals that balance control performance and attack detection. The proposed method asymptotically derives the optimal watermark for systems with unknown parameters.
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.