Performance safety enforcement in strongly connected timed event graphs

Abstract

In this paper, we tackle the performance safety enforcing problem in plants modeled by timed event graphs that are a subclass of timed Petri nets. We assume that a malicious intruder can increase the firing delay of transitions by adding delay in communication, or corrupt the transmitted data. Our target is to design a transition protecting policy to guarantee that the global performance does not drop below a given lower-bound threshold. Two classes of situations are considered: (1) the operator does not know the capability of the intruder, which means that all possible attacks must be taken into account; (2) the operator knows the upper bound of the capability of the intruder, e.g., the maximal number of transitions that can be simultaneously attacked. For the former case, we develop an algorithm using mixed integer linear programming to obtain an optimal protecting policy. For the latter situation, we develop a heuristic method to compute a protecting policy that is locally optimal.