Vehicular PKI scalability-consistency trade-offs in large scale distributed scenarios

Intelligent Transport Systems (ITS) are becoming a mature technology: standardisation progress and pre-deployment projects are opening the way to smart mobility. Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) communications are paramount to cooperative awareness and safety applications, and must be protected. In recent years, a lot of research has been focusing on vehicular communication security and privacy. Current ITS communication security functionalities include message authentication, which has an impact on the privacy of vehicles and drivers. At the European level, the European Telecommunications Standards Institute (ETSI) has defined a message authentication mechanism based on a Public Key Infrastructure (PKI). In order to serve a huge amount of ITS Stations (ITS-Ss), the Vehicular Public Key Infrastructure (VPKI) has high scalability requirements. To the best of our knowledge, so far no one has investigated the VPKI scalability in large-scale deployment. In this paper, we present the first extensive measurement campaign of a fully functional ETSI-compliant PKI. In our measurement campaign we assess PKI performance and scalability, replicating the system on hundreds of machines. In particular, we evaluate different replication strategies in terms of performance and consistency implications.