A Sensor Watermarking Design for Threat Discimination

This paper proposes a sensor additive switching watermark methodology for detecting physical faults and replay attacks, and then identifying the occurring threat type: either the physical fault or the replay attack. The sensor watermark methodology includes a switching watermark generator in the plant side and a switching watermark remover in the control and monitoring side. The switching protocols of the generator and the remover and their common watermark seeds are specifically designed, guaranteeing the switch synchronization in both the nominal and fault cases, and allowing the switch asynchronization in the replay attack case. The latter is used for discriminating the two considered threat cases. The detectability and discrimination ability of the proposed watermark approach, characterizing the class of attacks and faults that can be detected and discriminated, is rigorously investigated. A simulation example is presented to illustrate the effectiveness of the proposed approach.