Towards a Constrained-based Verification of Parameterized Cryptographic Protocols

Although many works have been dedicated to standard pro- tocols like Needham-Schroeder very few address the more challenging class of group protocols. We present a synchronous model for group protocols, that generalizes standard protocol models by permitting un- bounded lists inside messages. In this extended model we propose a cor- rect and complete set of inference rules for checking security properties in presence of an active intruder for the class of well-tagged protocols. Our inference system generalizes the ones that are implemented in several tools for a bounded number of sessions and fixed size lists in message. In particular when applied to protocols whose specification does not con- tain unbounded lists our inference system provides a decision procedure for secrecy in the case of a fixed number of sessions.