In Hardware We Trust? From TPM to Enclave Computing on RISC-V

System-on-Chip platforms have been increasingly extended with trusted computing functionality to provide strong protection for sensitive software applications through enclaves that only require trust in the hardware and minimal software components. However, the deployed enclave architectures are still suffering from various shortcomings such as the lack of secure I/O, or being vulnerable to side-channel attacks. Thus, recent research works propose new enclave architectures with more comprehensive threat models and advanced security features. A majority of these solutions is being developed on the open RISC-V architecture. In this paper, we present a brief overview of the RISC-V-based enclave architectures, discuss their features, limitations and open challenges.