A Secure-by-Design Hardware/Operating System as a Substrate for Trustworthy Computing

Abstract

Nowadays, digital devices like sensors, cell phones, and home servers are deeply embedded in our world to make our daily lives easier. Since we heavily rely on these systems, it is crucial to guarantee their correct functionality and to ensure security and privacy properties. As systems become increasingly complex, it is difficult to maintain security since it necessitates a thorough understanding of all functionalities in hardware and software. Complexity may lead to vulnerabilities that malicious components can exploit. These components can compromise security features provided by the processing cores and the operating system (OS), jeopardizing the overall trustworthiness of the system. In this article, we provide a secure-by-default hardware/OS co-design to build a substrate for trustworthy computing in digital devices. The design is based on a tiled architecture that can integrate untrusted hardware components. Instead of relying on isolation mechanisms of potentially malicious components, isolation is achieved by dedicated and independent hardware components called trusted communication units (TCUs). By keeping the attack surface small and isolating all components by default, malicious hardware and software are restricted in access permissions and, hence, cannot easily break the system’s security. We implemented a TCU-based multiprocessor architecture in a silicon research chip, called Masur23, and ran transfer workloads and selected portions of the microkernel-based OS M³. Our measurements demonstrate the feasibility of such a hardware/OS co-design for trustworthy computing. Compared to the entire chip implementation, security features require minimal latency, area, and power consumption overhead.