SMEBE-CAN: Selective Multicast Encryption Enabled Broadcast Encryption for CAN 2.0B

Broadcast encryption schemes for the standard Controller Area Network (CAN 2.0B) reduce bandwidth for data transmission from one electronic control unit (ECU) to others while assuring confidentiality. If received data is damaged, CAN 2.0B enables remote transmission request (RTR), allowing recipient ECUs to request retransmissions. However, retransmission for n ECUs increases the communication cost of current broadcast encryption techniques to a complexity O(n) for intra-vehicular networks (IVNs). This paper designs a novel broadcast encryption called SMEBE-CAN that retains its sublinear complexity of $O(\sqrt {\text{n}} )$ throughout IVN retransmissions. Besides, we devise a robust authenticated key exchange (AKE) protocol using SMEBE-CAN to address IVN data corruption during regular communication. Our protocol is provably secure in the standard model under the harness of the bilinear Diffie-Hellman exponent (BDHE) assumption. Besides, it is formally verified using the Scyther tool. As proof of concept, a performance comparison for 100 ECUs, with 10 ECUs per group, shows that the SMEBE-CAN has a lower authentication delay when ECUs are run at higher frequencies. Nonetheless, it ensures a lower bus load than related schemes, making it fit for practical usage.