Trusted Hart for Mobile RISC-V Security

Abstract

This paper addresses the critical need for a robust Trusted Execution Environment (TEE) within future RISC-V mobile devices, contrasting with the established Arm security architecture. The authors propose a novel security architecture that extends the open-source Keystone framework by introducing a dedicated core known as the "Trusted Hart." This Trusted Hart runs a privileged operating system dedicated to managing essential security functions, such as the device's keystore and secure peripherals, while maintaining compatibility with the GlobalPlatform TEE API specification.

Report

Key Highlights

• Mobile Security Focus: Aims to replicate and improve upon the standard TEE capabilities found in Arm-based mobile architectures for the RISC-V ecosystem.
• Trusted Hart Innovation: Introduces the concept of a "Trusted Hart"—a normal core dedicated solely to running a trusted operating system for core security functions.
• Standard Compliance: The proposed architecture supports the industry-standard GlobalPlatform TEE API for trusted applications.
• Keystone Integration: Identifies and addresses security gaps in the open-source Keystone framework for building custom TEEs.
• Experimental Verification: The architecture was validated experimentally using the HiFive Unleashed RISC-V development board.

Technical Details

• Security Architecture: The system combines Keystone enclaves with the dedicated Trusted Hart to achieve a comprehensive TEE solution for RISC-V System-on-a-Chips (SoCs).
• Trusted Hart Role: The dedicated core runs a trusted operating system responsible for high-security tasks, specifically mentioned as controlling the device's keystore and managing secure peripherals.
• Base Framework: The architecture builds upon and modifies the existing open-source Keystone framework.
• API Support: Ensures backward and forward compatibility for trusted applications by supporting the standardized GlobalPlatform TEE API specification.
• Verification Platform: The physical verification and testing were carried out on the HiFive Unleashed development board, confirming the practical implementability of the design.

Implications

• Accelerating RISC-V in Mobile: Provides a crucial, validated security foundation necessary for RISC-V to be viable in security-sensitive markets, particularly mobile phones and consumer electronics, where TEEs are mandatory.
• Standardized Security: Support for the GlobalPlatform TEE API significantly lowers the barrier to entry for developers, allowing the migration or creation of trusted applications using established industry standards.
• Ecosystem Enhancement: By extending and fortifying Keystone, the paper contributes significant architectural improvements to the open-source RISC-V security stack.
• Architectural Flexibility: The concept of dedicating a standard core (Hart) to security offers a modular and potentially resource-efficient approach to partitioning trusted and untrusted environments.