Enforcing Degree of Opacity with Supervisory Control
Bryony H. Schonewille, Richard Hugh Moulton, Karen Rudie · 2022 IEEE 61st Conference on Decision and Control (CDC) · 2022
The opacity-enforcement problem in discrete-event systems is one of ensuring that an adversarial observer cannot determine a given system’s secret. Although the problem has been well studied, existing formulations enforce opacity as a binary notion: a system is either opaque or it isn’t. Here we introduce a more general measure of a system’s opacity called degree of opacity. This measure can be used to assess the security of systems with respect to different criteria through the quantification of the level of security. We demonstrate how the subobserver property allows supervisory control to produce a closed-loop system whose overall degree of opacity meets a desired threshold. We demonstrate that degree of opacity can be used in place of the traditional, binary definition and argue that many applications will benefit from this nuanced view.