Paper 2025/508

Towards Building Scalable Constant-Round MPC from Minimal Assumptions via Round Collapsing

Abstract

In this work, we study the communication complexity of constant-round secure multiparty computation (MPC) against a fully malicious adversary and consider both the honest majority setting and the dishonest majority setting. In the (strong) honest majority setting (where $t=(1/2-ϵ)n$ for a constant $ϵ$), the best-known result without relying on FHE is given by Beck et al. (CCS 2023) based on the LPN assumption that achieves $$ communication, where $$ is the security parameter and the achieved communication complexity is independent of the number of participants. In the dishonest majority setting, the best-known result is achieved by Goyal et al. (ASIACRYPT 2024), which requires $$ bits of communication and is based on the DDH and LPN assumptions. In this work, we achieve the following results: (1) For any constant $$, we give the first constant-round MPC in the dishonest majority setting for corruption threshold $$ with $$ communication assuming random oracles and oblivious transfers, where $$ is the circuit depth. (2) We give the first constant-round MPC in the standard honest majority setting (where $$) with $$ communication only assuming random oracles. Unlike most of the previous constructions of constant-round MPCs that are based on multiparty garbling, we achieve our result by letting each party garble his local computation in a non-constant-round MPC that meets certain requirements. We first design a constant-round MPC that achieves $$ communication assuming random oracles in the strong honest majority setting of $$. Then, we combine the party virtualization technique and the idea of MPC-in-the-head to boost the corruption threshold to $$ for any constant $$ assuming oblivious transfers to achieve our first result. Finally, our second result is obtained by instantiating oblivious transfers using a general honest-majority MPC and the OT extension technique built on random oracles.