SecTEE: A Software-based Approach to Secure Enclave Architecture Using TEE

Secure enclaves provide a practical solution to secure computation, and current approaches to secure enclaves are implemented by extending hardware security mechanisms to the CPU architecture. Therefore, it is hard for a platform to offer secure computation if its CPU architecture is not equipped with any secure enclave features. Unfortunately, ARM CPUs, dominating mobile devices and having increasing momentum in cloud markets, do not provide any security mechanisms achieving the security equivalent to modern secure enclave architectures. In this paper, we propose SecTEE, a software-based secure enclave architecture which is based on the CPU's isolation mechanism and does not require specialized security hardware of the CPU architecture such as memory encryption engines. SecTEE achieves a high level of security even compared with hardware-based secure enclave architectures: resistance to privileged host software attacks, lightweight physical attacks, and memory access based side-channel attacks. Besides, SecTEE provides rich trusted computing primitives for enclaves: integrity measurement, remote attestation, data sealing, secrets provisioning, and life cycle management. We implement a SecTEE prototype based on the ARM TrustZone technology, but our approach can be applied to other CPU architectures with isolation mechanisms. The evaluation results show that most overhead comes from the software encryption and the runtime overhead imposed by trusted computing primitives is acceptable.