Using Implicit Certification to Efficiently Establish Authenticated Group Keys for In-Vehicle Networks

In the last years, researchers have exposed vulnerabilities on modern road vehicles that may have severe safety implications. Specifically, the most popular in-vehicle communication protocol CAN is prone to spoofing attacks. As a consequence, various security frameworks have been published, in order to both authenticate and encrypt data on vehicular buses. However, key management has often been neglected. Cryptographic keys are frequently hard coded, their authenticity is not verified and key updates are not possible at all. Contemporary ECUs are usually resource-constrained devices without the necessary hardware support to securely store cryptographic keys. This is why lightweight techniques for regular key updates are required. In this work, we use implicit certificates to derive authenticated message-based group keys for ECUs. These keys can subsequently be used for authentication and encryption as proposed in already existing works. In case a key gets corrupted, our approach enables fast key updates. We implement the proposed lightweight scheme on constrained devices that are connected over CAN, hence proving that our solution is applicable for the automotive domain. Our measurements show that a key update takes roughly 27ms after initialization.