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. We present DRAMatic, which implements operations foundational to HE on UPMEM PIM -- a programmable general-purpose PIM system developed by UPMEM. 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. It achieves a 334 times speed-up compared to previous HE implementations on UPMEM PIM. We also 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 Microsoft SEAL and HE implementations on UPMEM PIM. However, we also show that DRAMatic is currently constrained by data transfer overhead and limited multiplication performance on UPMEM PIM hardware. Finally, we discuss potential hardware extensions to UPMEM PIM.

翻译：同态加密（HE）是一种有前景的机密云计算技术，它允许对加密数据进行计算。然而，在传统计算机架构上，HE计算开销大且常受限于内存带宽。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能提供比传统架构更高的内存带宽，因此适合加速HE。我们提出DRAMatic，它在UPMEM PIM（一种由UPMEM开发的可编程通用PIM系统）上实现了HE的基础运算。DRAMatic集成了多种算术优化技术，包括余数系统（RNS）和数论变换（NTT）方法，能够支持安全同态评估所需的大参数。与先前在UPMEM PIM上的HE实现相比，它实现了334倍的加速。我们还将DRAMatic与流行的开源HE库Microsoft SEAL进行了运行时和能量效率对比评估。结果表明，DRAMatic显著缩小了Microsoft SEAL与UPMEM PIM上HE实现之间的性能差距。然而，我们也发现DRAMatic目前受限于UPMEM PIM硬件上的数据传输开销和乘法性能瓶颈。最后，我们讨论了UPMEM PIM潜在的可扩展硬件方案。