Enclave Application Cache for RISC-V Keystone

The development of the IoT society and the spread of cloud computing have also increased the number of insecure devices and vulnerable host OSs. We must protect the applications that deal with sensitive information, even from untrusted OSs. Trusted execution environment (TEE) technologies have attracted much attention because they enable an isolated, secure program execution environment from OSs. However, the booting phase of application execution in a TEE requires an expensive hash calculation in the measurement process for its executable binary image to guarantee its integrity. To mitigate this overhead, this paper proposes an enclave application cache mechanism for RISC-V Keystone, a representative RISC-V TEE. It bypasses the measurement process by storing the previously executed binary image in a secure memory space. The performance evaluation shows the proposed cache can achieve a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$6-40 \times$</tex> speedup in a TEE application's execution time.