Opacity problems in multi-energy timed automata

TL;DR

This paper investigates the challenge of verifying information leakage (opacity) in cyber-physical systems with continuous time and energy variables, introducing a new automata model and analyzing its decidability under various observation scenarios.

Contribution

It introduces guarded multi-energy timed automata, extending timed automata with multiple energy variables and guards, and studies their opacity verification under different attacker observation models.

Findings

Decidability results for subclasses with specific observation capabilities

Undecidability of the general formalism

Positive results when attacker observes final energy or execution time

Abstract

Cyber-physical systems can be subject to information leakage; in the presence of continuous variables such as time and energy, these leaks can be subtle to detect. We study here the verification of opacity problems over systems with observation over both timing and energy information. We introduce guarded multi-energy timed automata as an extension of timed automata with multiple energy variables and guards over such variables. Despite undecidability of this general formalism, we establish positive results over a number of subclasses, notably when the attacker observes the final energy and/or the execution time, but also when they have access to the value of the energy variables every time unit.