Trifecta: Faster High-throughput Three-party Computation over WAN using Multi-fan-in Logic Gates

Abstract

Multi-party computation (MPC) has been a very active area of research and recent industrial deployments exist. Practical MPC is currently limited to low-latency, high- throughput network setups, i.e., local-area networks (LAN). However, many use cases require the participation of different entities located in different data centers, i.e., communication over wide-area networks (WAN). Although, constant-round MPC exists, it has very high communication cost. In contrast, protocols based on secret-sharing are suitable for efficient parallelization but their running time is limited by the network latency. In this work, we investigate the reduction of the round complexity of secret-shared based multi-party computation. We propose a new three-party computation protocol that allows to compute multi-fan-in AND gates in one round of communication without any preprocessing. Using this primitive, we describe depth-optimized constructions for major building blocks in multi-party computation including addition, multiplication and comparison. We demonstrate the increased performance of our approach by evaluating several such functionalities in a real WAN environment. For the common benchmark of AES, our protocol achieves subsecond running time for all key lengths of AES over WAN, outperforming even constant-round protocols. We also improve upon state-of-the-art secret-shared based protocols in terms of throughput. For example, we observe that our protocol has a higher throughput by a factor of 2.2× compared to the best previous work. Our work shows that it is possible to have fast high-throughput multi-party computation with practical applications between parties in distant global regions.