Authentication and Key Distribution for SAE J1939 CAN Bus Without Security-Designated ECU

As a higher-layer protocol over a controller area network (CAN) or CAN with a flexible data-rate bus, Society of Automotive Engineers (SAE) J1939 has been widely adopted in commercial vehicles. Although it supports advanced diagnostics, complex data transmission, and network management in harsh environments, SAE J1939 lacks native authentication mechanisms. Consequently, in-vehicle communication remains vulnerable to replay, spoofing, and injection attacks. In practice, deploying a Security-designated Electronic Control Unit (SeCU) is often deemed necessary to provide robust authentication, as generating and distributing session keys is essential. However, this introduces a single point of failure and renders the SeCU a high-value target for attackers. To address these issues, we propose J1939-ADBE, an authentication and key-distribution scheme that operates without a centralized SeCU. The scheme is built on Authenticated Distributed Broadcast Encryption (ADBE), a tightly integrated construction that augments distributed broadcast encryption with publicly verifiable sender authentication in a shared bilinear setting. By leveraging ADBE, we eliminate the requirement for a SeCU while achieving the desired security goals. Using the Tamarin Prover, we formally verify in the Dolev–Yao model that J1939-ADBE satisfies injective agreement, session secrecy, known-key security, and forward secrecy. Furthermore, the broadcast nature of ADBE reduces the communication cost of key distribution from O(n) to O(|G|), where n denotes the number of Electronic Control Units (ECUs) and |G| denotes the number of ECU logical groups. Experimental results show that our proposal is practical for authentication within SAE J1939 networks.