  Over-the-Air (OTA) software updates are becoming essential for
electric/electronic vehicle architectures in order to reduce recalls amid the
increasing software bugs and vulnerabilities. Current OTA update architectures
rely heavily on direct cellular repository-to-vehicle links, which makes the
repository a communication bottleneck, and increases the cellular bandwidth
utilization cost as well as the software download latency. In this paper, we
introduce ScalOTA, an end-to-end scalable OTA software update architecture and
secure protocol for modern vehicles. For the first time, we propose using a
network of update stations, as part of Electric Vehicle charging stations, to
boost the download speed through these stations, and reduce the cellular
bandwidth overhead significantly. Our formalized OTA update protocol ensures
proven end-to-end chain-of-trust including all stakeholders: manufacturer,
suppliers, update stations, and all layers of in-vehicle Electric Control Units
(ECUs). The empirical evaluation shows that ScalOTA reduces the bandwidth
utilization and download latency up to an order of magnitude compared with
current OTA update systems.
