Fully homomorphic encryption allows the evaluation of arbitrary functions on encrypted data. It can be leveraged to secure outsourced and multiparty computation. TFHE is a fast torus-based fully homomorphic encryption scheme that allows both linear operations, as well as the evaluation of arbitrary non-linear functions. It currently provides the fastest bootstrapping operation performance of any other FHE scheme. Despite its fast performance, TFHE suffers from a considerably higher computational overhead for the evaluation of homomorphic circuits. Computations in the encrypted domain are orders of magnitude slower than their unencrypted equivalents. This bottleneck hinders the widespread adoption of (T)FHE for the protection of sensitive data. While state-of-the-art implementations focused on accelerating and outsourcing single operations, their scalability and practicality are constrained by high memory bandwidth costs. In order to overcome this, we propose an FPGA-based hardware accelerator for the evaluation of homomorphic circuits. Specifically, we design a functionally complete TFHE processor for FPGA hardware capable of processing instructions on the data completely on the FPGA. In order to achieve a higher throughput from our TFHE processor, we implement an improved programmable bootstrapping module which outperforms the current state-of-the-art by 240\% to 480\% more bootstrappings per second. Our efficient, compact, and scalable design lays the foundation for implementing complete FPGA-based TFHE processor architectures.

翻译：全同态加密允许对加密数据执行任意函数运算，可用于保障外包计算与多方计算的安全性。TFHE是一种基于环面的快速全同态加密方案，既能执行线性运算，也能评估任意非线性函数。目前该方案在所有FHE方案中具有最快的自举运算性能。尽管性能优异，TFHE在同态电路评估方面仍面临较高的计算开销，其加密域运算速度较非加密等效运算慢数个数量级。这一瓶颈阻碍了(T)FHE在敏感数据保护领域的广泛应用。虽然现有前沿实现方案专注于加速和外包单一运算，但其可扩展性与实用性受限于高昂的内存带宽成本。为突破此限制，我们提出一种基于FPGA的同态电路评估硬件加速器。具体而言，我们设计了一款功能完备的TFHE处理器，该处理器完全在FPGA硬件上执行数据指令处理。为实现更高吞吐量，我们实现了改进型可编程自举模块，其每秒自举运算次数较当前最优方案提升240%至480%。我们高效、紧凑且可扩展的设计为构建完整的基于FPGA的TFHE处理器架构奠定了基础。