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 networked discrete event systems (NDESs), the DESs run in a shared network, and the communication delays and losses are inevitable usually. In this paper, we investigate the problems of opacity in the framework of NDESs. We formulate four kinds of opacity for NDESs, including current-state opacity, initial-state opacity, initial-final-state opacity, and K-step opacity. We also present the verification algorithms for these notions. We extend the notions of opacity in classical DESs, that is, if the communication delays and losses disappear, then these new notions would reduce to their classical counterparts. A number of examples are provided to illustrate the results obtained. (C) 2020 Elsevier Inc. All rights reserved.

Automated summary

This paper investigates the opacity problems in networked discrete event systems (NDESs), formulating four kinds of opacity for NDESs and presenting verification algorithms for these notions. The extension of opacity notions in classical DESs suggests that when communication delays and losses disappear, the new notions will reduce to their classical counterparts.