1. [Publications](/publications)
2. GPIR: Enabling Practical Private Information Retrieval with GPUs

 # GPIR: Enabling Practical Private Information Retrieval with GPUs

  ![Publication image](/sites/default/files/styles/wide/public/default_images/default.jpeg?itok=TfIobf92 "Publication image")

 Private information retrieval (PIR) allows private database queries; however, it is hindered by intense server-side computation and memory traffic. Numerous modern lattice-based PIR protocols consist of three phases: ExpandQuery (expanding a query into encrypted indices), RowSel (encrypted row selection), and ColTor (recursive "column tournament" for final selection). ExpandQuery and ColTor primarily perform number-theoretic transforms (NTTs), whereas RowSel reduces to large-scale independent matrix-matrix multiplications (GEMMs). GPUs are well suited for these tasks when combined with multi-client batching, which is necessary for high throughput. However, batching fundamentally reshapes the performance bottlenecks: while it amortizes database access costs, it expands working sets beyond the L2 cache capacity, causing divergent memory access behavior and excessive DRAM traffic. We present GPIR, a GPU-accelerated PIR system that rethinks kernel design, data layout, and execution scheduling. We introduce a stage-aware hybrid execution model that dynamically switches between operation-level kernels, which execute each primitive operation separately, and stage-level kernels, which fuse all operations within a stage into a single kernel to maximize on-chip data reuse. For RowSel, we resolve the mismatch between NTT-driven layouts and tiled GEMMs using a transposed-layout design with fine-grained pipelining. We further extend GPIR to multi-GPU systems, scaling throughput and database capacity with negligible communication overhead. GPIR achieves up to 297.2x higher throughput than PIRonGPU, the state-of-the-art GPU implementation.

 ## Authors

Hyesung Ji (Seoul National University)

Hyunah Yu (Seoul National University)

Jongmin Kim (Seoul National University)

Wonseok Choi (Seoul National University)

[Edward Suh](/person/edward-suh)

Jung Ho Ahn (Seoul National University)

 ## Publication Date

Monday, April 6, 2026

 ## Published in

[Arxiv](https://arxiv.org/abs/2604.04696)

 ## Research Area

[Security](/research-area/security)