When It’s All Just Too Much: Outsourcing MPC-Preprocessing

Abstract

Many modern actively secure multi-party computation protocols make use of a function- and input-independent pre-processing phase. This pre-processing phase is tasked with producing some form of correlated randomness and distributing it to the parties. Whilst the “online” phase of such protocols is exceedingly fast, the bottleneck comes in the pre-processing phase. In this paper we examine situations in which the computing parties in the online phase may want to outsource the pre-processing phase to another set of parties, or to a sub-committee. We examine how this can be done, and also describe situations where this may be a benefit.