  Vehicular networks will enable a range of novel applications to enhance road
traffic efficiency, safety, and reduce fuel consumption. As for other
cyber-physical systems, security is essential to the deployment of these
applications and standardisation efforts are ongoing. In this paper, we perform
a systematic security evaluation of a vehicular platooning protocol through a
thorough analysis of the protocol and security standards. We tackle the
complexity of the resulting model with a proof strategy based on a relation on
keys. The key relation forms a partial order, which encapsulates both secrecy
and authenticity dependencies. We show that our order-aware approach makes the
verification feasible and proves strong authenticity properties along with
secrecy of all keys used throughout the protocol.
