A Bisimilarity Congruence for the Applied pi-Calculus Sufficiently Coarse to Verify Privacy Properties

Abstract

This paper is the first thorough investigation into the coarsest notion of bisimilarity for the applied π -calculus that is a congruence relation: open barbed bisimilarity. An open variant of labelled bisimilarity (quasi-open bisimilarity), better suited to constructing bisimulations, is proven to coincide with open barbed bisimilarity. These bisimilary congruences are shown to be characterised by an intuitionistic modal logic that can be used, for example, to describe an attack on privacy whenever a privacy property is violated. Open barbed bisimilarity provides a compositional approach to verifying cryptographic protocols, since properties proven can be reused in any context, including under input prefix. Furthermore, open barbed bisimilarity is sufficiently coarse for reasoning about security and privacy properties of cryptographic protocols; in constrast to the finer bisimilarity congruence, open bisimilarity, which cannot verify certain privacy properties.

Discovering ePassport Vulnerabilities using Bisimilarity

“…Remark 3.5. We explicitly include the word classical when we refer to classical FM, since there is an intuitionistic FM [HALT18,Hor18] The only reason we use early bisimilarity in this paper is in order to prove that the attack discovered closes the original problem. In short, we advocate quasi-open bisimilarity for checking privacy properties; but acknowledge the community must first be convinced that the methodology proposed solves established problems.…”