Opacity Enforcing Supervisory Control using Non-deterministic Supervisors

Abstract

Abstract In this paper, we investigate the enforcement of opacity via supervisory control in the context of discrete-event systems. A system is said to be opaque if the intruder, which is modeled as a passive observer, can never infer confidentially that the system is at a secret state. The design objective is to synthesize a supervisor such that the closed-loop system is opaque even though the control policy is publicly known. We propose to use non-deterministic supervisors, provides a set of control decisions at each instant, to enforce opacity. Such a non-deterministic control mechanism can enhance the plausible deniability of the controlled system as the online control decision cannot be implicitly inferred from the control policy. We provide an effective approach to synthesize a non-deterministic opacity-enforcing supervisor. We show that non-deterministic supervisors are strictly more powerful than deterministic supervisors.