An Output-Coding-Based Detection Scheme against Replay Attacks in Cyber-Physical Systems

This brief studies the detection problem of replay attacks against measurement data transmitted over the feedback channel of a cyber-physical system. In order to detect such replay attacks, an output coding scheme, where the control input is coded into the measurement output transmitted in the feedback channel, is proposed to make the output residuals between the normal and compromised cases significantly different, which thus triggers an alarm from an anomaly detector. The main advantage of this scheme is that the system performance in the normal situation is not affected compared with existing coding detection schemes, which is also the practical motivation of our work. In addition, the encoded measurement output is directly used to estimate the system state instead of setting a decoder. Both theoretical analysis and simulation results are provided to demonstrate the effectiveness of the proposed scheme.