The eXtensible Access Control Markup Language (XACML) is a popular OASIS standard for the specification of fine-grained access control policies. However, the standard does not provide a proper solution for the verification of XACML access control policies before their deployment. The first step for the formal verification of XACML policies is to formally specify such policies. Hence, this paper presents XACML2mCRL2, a tool for the automatic translation of XACML access control policies into mCRL2. The mCRL2 specifications generated by our tool can be used for formal verification of important properties of access control policies such as completeness of inconsistency, using the well-known mCRL2 toolset.

In recent years, it has come to attention that governments have been doing mass surveillance of personal communications without the consent of the citizens. As a consequence of these revelations, developers have begun releasing new protocols for end-to-end encrypted conversations, extending and making popular the old Off-the-Record protocol. New implementations of such end-to-end encrypted messaging protocols have appeared, and several popular chat applications have been updated to use such protocols. In this survey, we compare six existing applications for end-to-end encrypted instant messaging, namely, Signal, WhatsApp, Wire, Viber, Riot, and Telegram, most of them implementing one of the recent and popular protocols called Signal. We conduct five types of experiments on each of the six applications using the same hardware setup. During these experiments, we test 21 security and usability properties specially relevant for applications (not protocols). The results of our experiments demonstrate that the applications vary in terms of the usability and security properties they provide, and none of them are perfect. In consequence, we make 12 recommendations for improvement of either security, privacy, or usability, suitable for one or more of the tested applications.