Private information retrieval (PIR) is an essential cryptographic protocol for privacy-preserving applications, enabling a client to retrieve a record from a server's database without revealing which record was requested. Single-server PIR based on homomorphic encryption has particularly gained immense attention for its ease of deployment and reduced trust assumptions. However, single-server PIR remains impractical due to its high computational and memory bandwidth demands. Specifically, reading the entirety of large databases from storage, such as SSDs, severely limits its performance. To address this, we propose IVE, an accelerator for single-server PIR with a systematic extension that enables practical retrieval from large databases using DRAM. Recent advances in DRAM capacity allow PIR for large databases to be served entirely from DRAM, removing its dependence on storage bandwidth. Although the memory bandwidth bottleneck still remains, multi-client batching effectively amortizes database access costs across concurrent requests to improve throughput. However, client-specific data remains a bottleneck, whose bandwidth requirements ultimately limits performance. IVE overcomes this by employing a large on-chip scratchpad with an operation scheduling algorithm that maximizes data reuse, further boosting throughput. Additionally, we introduce sysNTTU, a versatile functional unit that enhances area efficiency without sacrificing performance. We also propose a heterogeneous memory system architecture, which enables a linear scaling of database sizes without a throughput degradation. Consequently, IVE achieves up to 1,275x higher throughput compared to prior PIR hardware solutions.

翻译：私有信息检索（PIR）是隐私保护应用中的关键密码协议，它允许客户端从服务器的数据库中检索记录，而无需透露所请求的具体记录。基于同态加密的单服务器PIR因其易于部署和降低信任假设而受到广泛关注。然而，单服务器PIR由于其高计算和内存带宽需求，目前仍不实用。具体而言，从存储设备（如SSD）中读取整个大型数据库严重限制了其性能。为解决这一问题，我们提出了IVE，一种用于单服务器PIR的加速器，通过系统扩展实现了从大型数据库中使用DRAM进行实用检索。DRAM容量的最新进展使得大型数据库的PIR服务能够完全在DRAM中运行，消除了对存储带宽的依赖。尽管内存带宽瓶颈仍然存在，但多客户端批处理通过分摊并发请求的数据库访问成本，有效提高了吞吐量。然而，客户端特定数据仍是一个瓶颈，其带宽需求最终限制了性能。IVE通过采用具有操作调度算法的大型片上暂存器来最大化数据重用，进一步提升了吞吐量。此外，我们引入了sysNTTU，一种多功能功能单元，在不牺牲性能的情况下提高了面积效率。我们还提出了一种异构内存系统架构，支持数据库大小的线性扩展而不会降低吞吐量。因此，与先前的PIR硬件解决方案相比，IVE实现了高达1,275倍的吞吐量提升。