Overview of discrete event systems opacity: Models, validation, and quantification

Over the last decade, opacity of discrete event systems (DES) has become a very fertile field of research. Driven bysafety and privacy concerns in network communications and online services, much theoretical work has been conductedin order to design opaque systems. A system is opaque if an external observer in unable to infer a ”secret” about thesystem behavior. This paper aims to review the most commonly used techniques of opacity validation for deterministic models and opacity quantification for probabilistic ones. Available complexity results are also provided. Finally, wereview existing tools for opacity validation and current applications.