Expiring opacity problems in parametric timed automata

Étienne André (1, 2) , Engel Lefaucheux (3, 4, 5) , Dylan Marinho (3, 4, 5)

1 Université Sorbonne Paris Nord
2 LIPN - Laboratoire d'Informatique de Paris-Nord
3 LORIA - Laboratoire Lorrain de Recherche en Informatique et ses Applications
4 Inria Nancy - Grand Est
5 UL - Université de Lorraine

Information leakage can have dramatic consequences on the security of real-time systems. Timing leaks occur when an attacker is able to infer private behavior depending on timing information. In this work, we propose a definition of expiring timed opacity w.r.t. execution time, where a system is opaque whenever the attacker is unable to deduce the reachability of some private state solely based on the execution time; in addition, the secrecy is violated only when the private state was visited "recently", i. e., within a given time bound (or expiration date) prior to system completion. This has an interesting parallel with concrete applications, notably cache deducibility: it may be useless for the attacker to know the cache content too late after its observance. We study here expiring timed opacity problems in timed automata. We consider the set of time bounds (or expiration dates) for which a system is opaque and show when they can be effectively computed for timed automata. We then study the decidability of several parameterized problems, when not only the bounds, but also some internal timing constants become timing parameters of unknown constant values.

Mots clés: timed opacity; security; Timed automata

Domaines: Informatique [cs]

Étienne André, Engel Lefaucheux, Dylan Marinho. Expiring opacity problems in parametric timed automata. 2023 27th International Conference on Engineering of Complex Computer Systems (ICECCS), Jun 2023, Toulouse, France. pp.89-98, ⟨10.1109/ICECCS59891.2023.00020⟩. ⟨hal-04151207v2⟩