TRICKS—Time TRIggered Covert Key Sharing for Controller Area Networks

There are dozens of proposals for securing the controller area network (CAN); however, only a few of them are concerned on how to share secret keys between CAN nodes. Recently, some works have used the non-destructive property of CAN arbitration in order to exchange a secret key and achieve information theoretic security for the key exchange. In our proposals, we exploit both delays and the non-destructive arbitration of CAN to achieve a secure key exchange. While our approach is less efficient when it comes to bandwidth, we do not require any kind of additional hardware and we build our implementation on the software layer which is accessible for any CAN-based application. To boost efficiency, we finally bootstrap secret keys by means of the guessing-resilient protocols, such as encrypted-key-exchange (EKE) and simple password exponential key exchange (SPEKE). In principle, a few dozen frames suffice for a secure key-exchange between two CAN nodes. We discuss several protocol versions and extensions for the case of more than two parties. We also present the experimental results on modern automotive-grade controllers to prove the performance of our solution.