  Secure multi-party computation (MPC) allows parties to perform computations
on data while keeping that data private. This capability has great potential
for machine-learning applications: it facilitates training of machine-learning
models on private data sets owned by different parties, evaluation of one
party's private model using another party's private data, etc. Although a range
of studies implement machine-learning models via secure MPC, such
implementations are not yet mainstream. Adoption of secure MPC is hampered by
the absence of flexible software frameworks that "speak the language" of
machine-learning researchers and engineers. To foster adoption of secure MPC in
machine learning, we present CrypTen: a software framework that exposes popular
secure MPC primitives via abstractions that are common in modern
machine-learning frameworks, such as tensor computations, automatic
differentiation, and modular neural networks. This paper describes the design
of CrypTen and measure its performance on state-of-the-art models for text
classification, speech recognition, and image classification. Our benchmarks
show that CrypTen's GPU support and high-performance communication between (an
arbitrary number of) parties allows it to perform efficient private evaluation
of modern machine-learning models under a semi-honest threat model. For
example, two parties using CrypTen can securely predict phonemes in speech
recordings using Wav2Letter faster than real-time. We hope that CrypTen will
spur adoption of secure MPC in the machine-learning community.
