Replay Attack Detection using Switching Multi-sine Watermarking

This paper examines the detection of replay attack in a control system that is in steady state at some operating point. A watermarking scheme based on switching multi-sine waves is proposed in which the controller adds the watermark to the control signal and monitors the corresponding effects on sensor readings received through a communication channel. The frequencies of sinusoids are changed frequently to prevent the attacker from replicating the effects of watermarking in the system output. Switching sinusoids could generate undesirable transient responses. This paper presents a procedure to choose an appropriate number of sinusoidal terms, and relative amplitudes and phases for the sine waves, to prevent such undesirable transients. The presence (or absence) of watermarking signal in the output is examined using power spectral density estimation.