Comparative Analysis and Implementation of Jump Address Masking for Preventing TEE Bypassing Fault Attacks

Attacks on embedded devices continue to evolve with the increasing number of applications in actual products. A trusted execution environment (TEE) enhances the security of embedded devices by isolating and protecting sensitive applications such as cryptography from malicious or vulnerable applications. However, the emergence of TEE bypass attacks using faults exposes TEEs to threats. In CHES'22, jump address masking (JAM) was proposed as a countermeasure against TEE bypass attacks, specifically targeting RISC-V. JAM prevents modifications of protected data by calculating jump addresses using the protected data, and is expected to provide promising resistance to TEE bypass attacks, for which traditional countermeasures are ineffective. However, JAM was originally proposed for bare metal applications. Therefore, its application to TEEs that operate with an OS presents technical and security challenges. This study proposes a method for applying JAM to Keystone, a major TEE framework for RISC-V, and validates its practical effectiveness and performance through a comparative evaluation with existing countermeasures such as memory encryption, random delays, and instruction duplication. Our evaluation reveals that the proposed JAM implementation is the first countermeasure that achieves complete resistance to TEE bypass attacks with an execution time overhead of approximately 340% for context switches and 1.0% across the entire program, which is acceptable compared with other countermeasures.