Discovering ePassport Vulnerabilities using Bisimilarity

Abstract

We uncover privacy vulnerabilities in the ICAO 9303 standard implemented by ePassports worldwide. These vulnerabilities, confirmed by ICAO, enable an ePassport holder who recently passed through a checkpoint to be reidentified without openning their ePassport. This paper explains how bisimilarity was used to discover these vulnerabilities. In order to tackle such bisimilarity problems, we develop here a chain of methods for the applied π-calculus including a symbolic under approximation of bisimilarity, called open bisimilarity, and a modal logic, called classical FM, for describing and certifying attacks. Evidence is provided to argue for a new scheme for specifying such unlinkability problems that more accurately reflects the capabilities of an attacker.