MT-SOTA: A Merkle-Tree-Based Approach for Secure Software Updates over the Air in Automotive Systems

Abstract

The automotive industry has seen a dynamic transformation from traditional hardware-defined to software-defined architecture enabling higher levels of autonomy and connectivity, better safety and security features, as well as new in-vehicle experiences and richer functions through software and ongoing updates of both functional and safety-critical features. Service-oriented architecture plays a pivotal role in realizing software-defined vehicles and fostering new business models for OEMs. Such architecture evolution demands new development paradigms to address the increasing complexity of software. This is crucial to guarantee seamless software development, integration, and deployment—all the way from cloud or backend repositories to the vehicle. Additionally, it calls for enhanced collaboration between car manufacturers and suppliers. Simultaneously, it introduces challenges associated with the necessity for ongoing updates and support ensuring vehicles remain safe and up to date. Current approaches to software updates have primarily been implemented for traditional vehicle architectures, which mostly comprise specialized electronic control units (ECUs) designed for specific functions. These ECUs are programmed with a single comprehensive executable that is then flashed onto the ECU all at once. Different approaches should be considered for new software-based vehicle architectures and specifically for ECUs with multiple independent software packages. These packages should be updated independently and selectively for each ECU. Thus, we propose a new scheme for software updates based on a Merkle tree approach to cope with the complexity of the new software architecture while addressing safety and security requirements of real-time and resource-constrained embedded systems in the vehicle. The Merkle-tree-based software updates over the air (MT-SOTA) proposal enables secure updates for individual software clusters. These clusters are developed and integrated by diverse entities with varying release timelines. Our study demonstrates that the MT-SOTA scheme can enhance the speed of software update execution without significantly increasing the process overhead. Additionally, it offers necessary defense against potential cyberthreats. The results of the performed technical analysis and experiments of the MT-SOTA implementation are presented in this paper.