Property-Based Transparency: a New Utility Definition*
Résumé
Cyber-physical systems (CPSs) are composed of computational and physical components that interact to achieve a desired behavior for a given system. These systems are widely used in industrial applications and have guaranteed a solid improvement in productivity. However, their high connectivity also makes them more vulnerable to cyber-attacks, and thus, strategies to increase and/or guarantee the privacy of classified information are mandatory. On the other hand, the availability of system information, known as utility, to trustworthy agents is fundamental to operating large-scale CPSs efficiently, which establishes a trade-off between the privacy of information against malicious agents and the utility of data to legitimate receivers. In this paper, we explore the utility problem for CPSs abstracted as Discrete-Event Systems (DESs), where the intended receiver must know useful information about the system to achieve a desired goal. In this context, we consider that this information is the ability to be sure when a given property of interest is satisfied before the system evolves to a state where this property is no longer valid. To this end, we propose a new utility notion called Property-Based Transparency (PT), and a method for verifying whether a system is transparent with respect to the desired property. In addition, we discuss PT's applicability in two domains and present how it relates to the notion of currentstate opacity and fault diagnosis of DES.