Protocol verification via rigid/flexible resolution

Abstract

We propose a decision procedure, i.e. an inference system for clauses containing rigid and flexible variables. Rigid variables are only allowed to have one instantiation, whereas flexible variables are allowed as many instantiations as desired. We assume a set of clauses containing only rigid variables together with a set of clauses containing only flexible variables. When the flexible clauses fall into a particular class, we propose an inference system based on ordered resolution that is sound and complete and for which the inference procedure will halt. An interest in this form of problem is for cryptographic protocol verification for a bounded number of protocol instances. Our class allows us to obtain a generic decidability result for a large class of cryptographic protocols that may use for instance CBC (Cipher Block Chaining) encryption and blind signature. © Springer-Verlag Berlin Heidelberg 2007.