Keystone: RISC-V Based Open-Source Secure Hardware Enclave

It's unlikely to be affected by spectre-like attack since Rocket chip based core doesn't have speculative exec.

https://riscv.org/2018/01/more-secure-world-risc-v-isa/ https://www.sifive.com/blog/2018/01/05/sifive-statement-on-m...