Opacity of Discrete Event Systems: models, validation and quantification

Abstract

International audienceOver the last decade, opacity of discrete event systems (DES) has become a very fertile field of research. Driven by safety and privacy concerns in network communications and online services, much theoretical work has been conducted in order to design opaque systems. A system is opaque if an external observer in unable to infer a " secret " about the system 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, we review existing tools for opacity validation and current applications

How to be sure a faulty system does not always appear healthy?

“…A very close research field worth comparing in a dedicated section is the opacity analysis of discrete event systems, introduced in 2005, which has become a very fertile field of research over the last decade, driven by safety and privacy concerns in network communications and online services (see [30] for a survey). A system is opaque if an external observer (the intruder) is unable to infer a "secret" about the system behavior, i.e., if for any secret behavior, there exists at least one other non-secret behavior that looks the same (for observation) to the intruder.…”

“…Different in its approach, SBO, introduced by [40] for automata, relates to the intruder ability to infer that the secret is or has been in a given secret state or set of states. Depending on the nature of the secret set, different SBO properties have been defined [30]. Thus one can distinguish among others Current-State Opacity (CSO), if the intruder can never infer, from its observations, whether the current state of the system is a secret state or not (i.e., for every trajectory that leads to a secret state, there exists another trajectory with same observation leading to a non-secret state) and Initial-State Opacity (ISO), if the intruder is never sure whether the system's initial state was a secret state or not (i.e., for every trajectory that originates from a secret initial state, there exists another trajectory with same observation originating from a non-secret initial state).…”

Detectability of networked discrete event systems

“…Another property related to detectability is opacity [65][66][67][68][69][70][71]. While detectability describes the ability to determine the states of a discrete event system, opacity describes the ability to hide the states or other information about a system.…”

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

“…In case of need, please refer to Cassandras & Lafortune (2008) for more information on these problems. This paper is an extended version of a paper presented by the authors at the 5 th IFAC International Workshop On Dependable Control of Discrete Systems (DCDS'15) (Jacob et al, 2015).…”