Interposer-Based Root of Trust

Industry is moving towards large-scale system-on-chip (SoC) designs where heterogeneous components such as processor cores, DSPs, memory controllers, and accelerator units are bundled via 2.5D integration. That is, these components are fabricated separately onto chiplets and then integrated using an interconnect carrier, a so-called interposer. Independently, however, general-purpose SoC architectures have raised significant security concerns. Therefore, with many IP modules and hardware components coming from various third-party vendors and manufacturers, ensuring security and integrity of chiplets-based system is a grand challenge. Further, malicious software running within a chiplet can pose significant risks as well. In this work, we propose to leverage an active interposer as secure-by-construction, generic root of trust platform for such modern systems. Our work presents a new architectural framework where untrusted processing elements, running untrusted code, are integrated on top of such an interposer-based root of trust, allowing us to detect and prevent any form of malicious messages exchanged between the heterogeneous components. Our technique has limited design overhead that is furthermore restricted to the active interposer, allowing the heterogeneous components within chiplets to remain untouched. We show that our scheme correctly handles attempted security violations with little impact on system performance, around 4%.