Opacity of Networked Discrete Event Systems

Opacity is an important information-flow property, which is used to characterize whether or not the secrets of system have been leaked to the intruders. Over the past ten years, opacity of discrete event systems (DESs) modeled as automata and Petri nets have been well investigated under the assumption that the communication channels between systems and intruders are perfect. However, in a shared network, the communication delays and losses are inevitable usually. In this paper, we investigate the problem of opacity of networked discrete event systems (NDESs). We propose the notions of current-state opacity, initial-state opacity, initial-final-state opacity, and infinite-step opacity for NDESs. We also present the verification algorithms for these notions. Some examples are provided to illustrate the results obtained.