Enhancing the Security of FPGA-SoCs via the Usage of ARM TrustZone and a Hybrid-TPM

Abstract

Isolated execution is a concept commonly used for increasing the security of a computer system. In the embedded world, ARM TrustZone technology enables this goal and is currently used on mobile devices for applications such as secure payment or biometric authentication. In this work, we investigate the security benefits achievable through the usage of ARM TrustZone on FPGA-SoCs. We first adapt Microsoft’s implementation of a firmware Trusted Platform Module (fTPM) running inside ARM TrustZone for the Zynq UltraScale+ platform. This adaptation consists in integrating hardware accelerators available on the device to fTPM’s implementation and to enhance fTPM with an entropy source derived from on-chip SRAM start-up patterns. With our approach, we transform a software implementation of a TPM into a hybrid hardware/software design that could address some of the security drawbacks of the original implementation while keeping its flexibility. To demonstrate the security gains obtained via the usage of ARM TrustZone and our hybrid-TPM on FPGA-SoCs, we propose a framework that combines them for enabling a secure remote bitstream loading. The approach consists in preventing the insecure usages of a bitstream reconfiguration interface that are made possible by the manufacturer and to integrate the interface inside a Trusted Execution Environment.