Attribute-based authorization tickets for Car-to-X communication

In this paper we propose an approach that allows an Intelligent Transportation System (ITS) Vehicle Station (IVS) to anonymously authenticate itself at applications with attribute-based access restrictions. For authentication purposes we apply attribute-based authorization tickets, which are granted after the IVS proved that it fulfills all access restrictions. For the proof of attributes we rely on Anonymous Credentials (ACs), which are sets of verified attributes. When proving attributes, only the ones necessary for the application are revealed, all others are kept private. The resulting system supports billing of application usage and revocation of an IVS, tickets, ACs, and single attributes, while protecting the privacy of the IVS. We propose two different versions of the system and present a prototype implementation. We furthermore compare their properties and evaluate the performance. We demonstrate that the additional time delay introduced by the proof of the attributes does not significantly influence the usability of the system.