Paper 2024/1919

PASTA on Edge: Cryptoprocessor for Hybrid Homomorphic Encryption

Abstract

Fully Homomorphic Encryption (FHE) enables privacy-preserving computation but imposes significant computational and communication overhead on the client for the public-key encryption. To alleviate this burden, previous works have introduced the Hybrid Homomorphic Encryption (HHE) paradigm, which combines symmetric encryption with homomorphic decryption to enhance performance for the FHE client. While early HHE schemes focused on binary data, modern versions now support integer prime fields, improving their efficiency for practical applications such as secure machine learning. Despite several HHE schemes proposed in the literature, there has been no comprehensive study evaluating their performance or area advantages over FHE for encryption tasks. This paper addresses this gap by presenting the first implementation of an HHE scheme- PASTA. It is a symmetric encryption scheme over integers designed to facilitate fast client encryption and homomorphic symmetric decryption on the server. We provide performance results for both FPGA and ASIC platforms, including a RISC-V System-on-Chip (SoC) implementation on a low-end 130nm ASIC technology, which achieves a 43–171$\times$ speedup compared to a CPU. Additionally, on high-end 7nm and 28nm ASIC platforms, our design demonstrates a 97$\times$ speedup over prior public-key client accelerators for FHE. We have made our design public and benchmarked an application to support future research.