MACsec has become a cornerstone for Ethernet-based in-vehicle network security, driven by the Open Alliance TC17’s specifications. Its line-rate integrity and HW-level implementations offer significant advantages over IPsec or TLS. A comparable Layer 2 security solution has been lacking for CAN. While SecOC is used, its incomplete standard hinders hardware implementations. To address this gap, we have, together with industry partners, initiated CANsec for CAN XL, heavily inspired by MACsec. After four years of security discussions, we changed our target. Let’s directly reuse MACsec for CANsec! This talk tells the story of adapting MACsec, detailing the challenges and solutions encountered. Furthermore, it provides an outlook on backporting CANsec, and thus MACsec, to CAN FD, enabling a unified security solution across Ethernet, CAN XL, and CAN FD. Attendees will gain insights into the evolution of MACsec beyond Ethernet and its potential to secure the entire in-vehicle network.