Attack Synthesis in Discrete Event Systems under Asymmetric Observation Setting

This work addresses the problem of cyber attack synthesis in discrete event systems modeled by finite state automata. A malicious attacker may modify an observation outputted from the considered system to confuse an operator who receives either the original observation or the corrupted observation of the system. Particularly, we assume that the attacker has fewer observable events than the operator, resulting in an asymmetric observation setting. This means that the attacker can only deduce the state estimation of the system based on its own observable events, not the observable event set of the system. A relation is defined as a pair of state estimations consistent with the original observation and corrupted observation from the attacker's perspective. A potentially harmful relation implies that the operator is confused in estimating the given critical states. This work aims to synthesize an attack to establish a potentially harmful relation while maintaining stealthiness. The attack synthesis problem is then considered as a two-player game structure between the operator and the attacker. Finally, an attack graph is constructed to illustrate all possible attack scenarios, and examples are provided to demonstrate the proposed attack strategy.