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On Handling of Certificate Digest in V2X Communication

We propose a change in the IEEE 1609.2 and ETSI ITS standards that define a certificate distribution mechanism, called inline peer-to-peer certificate distribution (P2PCD). Messages exchanged in V2X messages are secured with digital signatures and digital certificates for the corresponding public keys. This P2PCD mechanism is used in Basic Safety Message (BSM) for the US and Cooperative Awareness Message (CAM) for Europe, and allows vehicles to proactively resolve unknown certificates. The unknown certificate situation occurs as not all messages contain the certificate in order to reduce overhead in these messages. This mechanism appears to be beneficial to minimize delay in verifying the authenticity and integrity of received messages. We evaluated its usefulness by conducting a simulation to recreate real-world highway traffic flow. The result indicates that, for high-way traffic, the benefit of this mechanism is negligble. At the same time, it increases unnecessary processing burden in vehicles. Based on our observation, we propose to update the IEEE 1609.2 and ETSI ITS standards in such a way that this mechanism should be restricted to traffic environments where it brings benefits.