Typing messages for free in security protocols: the case of equivalence properties

Rémy Chrétien (1) , Véronique Cortier (2) , Stéphanie Delaune (1)

1 LSV - Laboratoire Spécification et Vérification [Cachan]
2 CASSIS - Combination of approaches to the security of infinite states systems

Our first main contribution is to reduce the search space for attacks. Specifically, we show that if there is an attack then there is one that is well-typed. Our result holds for a large class of typing systems and a large class of determinate security protocols. Assuming finitely many nonces and keys, we can derive from this result that trace equivalence is decidable for an unbounded number of sessions for a class of tagged protocols, yielding one of the first decidability results for the unbounded case. As an intermediate result, we also provide a novel decision procedure in the case of a bounded number of sessions.

Domaines: Cryptographie et sécurité [cs.CR]

Rémy Chrétien, Véronique Cortier, Stéphanie Delaune. Typing messages for free in security protocols: the case of equivalence properties. [Research Report] RR-8546, INRIA. 2014, pp.46. ⟨hal-01007580⟩