Orion: A Fully Homomorphic Encryption Compiler for Private Deep Neural Network Inference

Fully Homomorphic Encryption (FHE) has the potential to substantially improve privacy and security by enabling computation on encrypted data. This is especially true with deep learning, as today many popular user services are powered by neural networks. One of the major challenges facing wide-scale deployment of FHE-secured neural inference is effectively mapping them to the FHE domain. FHE poses many programming challenges including packing large vectors, handling expensive rotations, and correctly implementing complex strided convolutions. This makes programming FHE inferences prone to poor performance and errors. In this paper we overcome these challenges with Orion, an automated optimizing FHE compiler for neural inference. Orion automatically maps PyTorch-specified networks to FHE, handling common layer types and arbitrary tensor shapes and strides. Moreover, we develop novel optimizations that balance dense FHE vector packing, efficient rotations, and minimize operations to improve performance. We have implemented Orion, which will be open sourced, and evaluated it on common benchmarks used by the FHE deep learning community. We compare Orion to multiple state-of-the-art solutions and report iso-accuracy speedups ranging from 2.7$\times$ to 20.5$\times$.