Paper 2019/1104

More Efficient MPC from Improved Triple Generation and Authenticated Garbling

Kang Yang, Xiao Wang, and Jiang Zhang

Abstract

Recent works on distributed garbling have provided highly efficient solutions for constant-round MPC tolerating an arbitrary number of corruptions. In this work, we improve upon state-of-the-art protocols in this paradigm for further performance gain. First, we propose a new protocol for generating authenticated AND triples, which is a key building block in many recent works. -- We propose a new authenticated bit protocol in the two-party and multi-party settings from bare IKNP OT extension, allowing us to reduce the communication by about 24% and eliminate many computation bottlenecks. We further improve the computational efficiency for multi-party authenticated AND triples with cheaper and fewer consistency checks and fewer hash function calls. -- We implemented our triple generation protocol and observe around 4x to 5x improvement compared to the best prior protocol in most settings. For example, in the two-party setting with 10 Gbps network and 8 threads, our protocol can generate more than 4 million authenticated triples per second, while the best prior implementation can only generate 0.8 million triples per second. In the multi-party setting, our protocol can generate more than 37000 triples per second over 80 parties, while the best prior protocol can only generate the same number of triples per second over 16 parties. We also improve the state-of-the-art multi-party authenticated garbling protocol. -- We take the first step towards applying half-gates in the multi-party setting, which enables us to reduce the size of garbled tables by 2\kappa bits per gate per garbler, where \kappa is the computational security parameter. This optimization is also applicable in the semi-honest multi-party setting. -- We further reduce the communication of circuit authentication from 4\rho bits to 1 bit per gate, using a new multi-party batched circuit authentication, where \rho is the statistical security parameter. Prior solution with similar efficiency is only applicable in the two-party setting. For example, in the three-party setting, our techniques can lead to roughly a 35% reduction in the size of a distributed garbled circuit.