Homomorphic encryption (HE) is a promising technology for confidential cloud computing, as it allows computations on encrypted data. However, HE is computationally expensive and often memory-bound on conventional computer architectures. Processing-in-Memory (PIM) is an alternative hardware architecture that integrates processing units and memory on the same chip or memory module. PIM enables higher memory bandwidth than conventional architectures and could thus be suitable for accelerating HE. In this work, we present DRAMatic, which implements operations foundational to HE on UPMEM's programmable, general-purpose PIM system, and evaluate its performance. DRAMatic incorporates many arithmetic optimizations, including residue number system and number-theoretic transform techniques, and can support the large parameters required for secure homomorphic evaluations. To compare performance, we evaluate DRAMatic against Microsoft SEAL, a popular open-source HE library, regarding both runtime and energy efficiency. The results show that DRAMatic significantly closes the gap between UPMEM PIM and Microsoft SEAL. However, we also show that DRAMatic is currently constrained by UPMEM PIM's multiplication performance and data transfer overhead. Finally, we discuss potential hardware extensions to UPMEM PIM.

翻译：同态加密（HE）是一种用于机密云计算的前沿技术，它允许对加密数据进行计算。然而，在同态加密在传统计算机架构上计算成本高昂，且通常受限于内存带宽。内存处理（PIM）是一种替代性硬件架构，它将处理单元与内存集成在同一芯片或内存模块上。PIM能够提供比传统架构更高的内存带宽，因此可能适用于加速同态加密。在本工作中，我们提出了DRAMatic，它在UPMEM的可编程通用PIM系统上实现了同态加密的基础运算，并评估了其性能。DRAMatic融合了多种算术优化技术，包括余数系统和数论变换技术，并且能够支持安全同态求值所需的大参数。为了进行性能比较，我们从运行时间和能效两个方面，将DRAMatic与流行的开源同态加密库Microsoft SEAL进行了评估。结果表明，DRAMatic显著缩小了UPMEM PIM与Microsoft SEAL之间的性能差距。然而，我们也指出DRAMatic目前受到UPMEM PIM乘法性能和数据传输开销的限制。最后，我们讨论了UPMEM PIM潜在的硬件扩展方向。