Efficient certificate distribution for vehicle heartbeat messages

Vehicle heartbeat messages will enable a wide range of safety and efficiency applications. These messages, containing the position, kinematics, and state of a vehicle, will be sent over a wireless network to nearby vehicles at a high frequency. These messages will include a digital signature and a public key certificate to allow message recipients to validate the contents of a message. To minimize on the overhead, standards governing this network allow for the transmission of short certificate IDs instead of the full certificate. This paper proposes two distributed Certificate ID Scheduling algorithms, one in which a certificate is sent every nth message and another in which vehicles send full certificates only when a new neighbor is detected. Privacy considerations for certificate ID scheduling are analyzed, and the effectiveness of the protocols is evaluated through simulation of these heart-beat messages in a highway environment. These simulations show the first algorithm is most appropriate for high density, two-way traffic while the second algorithm can produce bandwidth savings that are close to the maximum for one-way or low density traffic.