Current-state opacity enforcement in discrete event systems under incomparable observations

In this paper we tackle the opacity enforcement problem in discrete event systems using supervisory control theory. In particular, we consider the case where the intruder and the supervisor may observe different sets of events and neither of these sets needs to be contained in the other one. Moreover, there may be controllable events that cannot be observed by the supervisor. We propose a finite structure, called an augmented I-observer, to characterize the strings that will not leak the secret. Based on such a structure, a locally optimal supervisor enforcing current-state opacity is designed.