Online / 6 & 7 February 2021

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Trusted RV: 64bit RISC-V TEE with Secure CoProcessor as Root of Trust


Trusted RV is a combination of 4 core 64bit RISC-V (AC: Application Core) and 1 core 32bit RISC-V Secure Coprocessor (SU: Secure Unit). The SU works as a "Root of Trust" and keeps critical information (e.g., Device Key, Certificate). The SU boots before the 64Bit RISC-V and controls it (i.e., secure boot, etc). The communication from the AC to the SU is limited for TEE (i.e., Keystone Encalve) only and keeps security. Trusted RV is implemented on an FPGA (Xilinx VC707) and a simulator.

We have developed the Trusted RV which is a combination of 4 core 64bit RISC-V and 1 core 32bit RISC-V Secure Coprocessor. The secure coprocessor works as a "Root of Trust" and keeps critical information (e.g., Device Key, Certificate). The secure coprocessor offers machine mode only and runs Zephyr OS. The Zephyr OS includes crypto and certificate-verification libraries and manages the 64bit RISC-V. The secure coprocessor boots before the 64bit RISC-V and verifies it.

The secure coprocessor is tightened with RISC-V Keystone on the 64bit RISC-V to keep security. The 64bit RISC-V runs Keystone as TEE (Trusted Execution Environment), and Secure Monitor (SM) runs on machine mode under the Linux kernel. The secure communication between 64bit RISC-V and Secure Coprocessor is managed by SM only. The communication is passed to a Trusted Application (TA) in a Keystone Enclave only. The secure communication is implanted on the shared memory and mutual interrupts between 64bit RISC-V and Secure Coprocessor. This mechanism is also used for the remote attestation of Keystone which based on the key in the secure coprocessor. The Trusted RV is implemented on a simulator for software development, as well as FPGA (Xilinx VC707).

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Photo of Kuniyasu Suzaki Kuniyasu Suzaki

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