  We present Virtual Secure Platform (VSP), the first comprehensive platform
that implements a multi-opcode general-purpose sequential processor over Fully
Homomorphic Encryption (FHE) for Secure Multi-Party Computation (SMPC). VSP
protects both the data and functions on which the data are evaluated from the
adversary in a secure computation offloading situation like cloud computing. We
proposed a complete processor architecture with a five-stage pipeline, which
improves the performance of the VSP by providing more parallelism in circuit
evaluation. In addition, we also designed a custom Instruction Set Architecture
(ISA) to reduce the gate count of our processor, along with an entire set of
toolchains to ensure that arbitrary C programs can be compiled into our custom
ISA. In order to speed up instruction evaluation over VSP, CMUX Memory based
ROM and RAM constructions over FHE are also proposed. Our experiments show that
both the pipelined architecture and the CMUX Memory technique are effective in
improving the performance of the proposed processor. We provide an open-source
implementation of VSP which achieves a per-instruction latency of less than 1
second. We demonstrate that compared to the best existing processor over FHE,
our implementation runs nearly 1,600$\times$ faster.

Cryptography and Security