  The use of vehicle-to-everything (V2X) communication is expected to
significantly improve road safety and traffic management. We present an
efficient protocol, called the AEE protocol, for protecting data authenticity
and user privacy in V2X applications. Our protocol provides event-based
likability, which enables messages from a subject vehicle to be linked to a
specific event in order to prevent Sybil attacks. Messages on different events
are unlinkable to preserve the long-term privacy of vehicles. Moreover, our
protocol introduces a new method for generating temporary public keys to reduce
computing and transmission overheads. Such a temporary public key is bound with
a certain event and is automatically revoked when the event is over. We
describe how to apply our protocol in vehicular communications using two
exemplar use cases. To further reduce the real-time computational complexity,
our protocol enables us to decompose the cryptographic operations into offline
processes for complex operations and real-time processes for fast computations.
