## Cryptology ePrint Archive: Report 2017/492

Reducing Communication Channels in MPC

Marcel Keller and Dragos Rotaru and Nigel P. Smart and Tim Wood

Abstract: In both information theoretic and computationally secure Multi-Party Computation (MPC) protocols the parties are usually assumed to be connected by a complete network of, respectively, secure or authenticated channels. Taking inspiration from a recent, highly efficient, 1-out-of-3 computationally secure MPC protocol of Araki et al, we show how to perform computationally secure MPC for an arbitrary $Q^2$ access structure over an incomplete network. Our tool is to combine the practical techniques of Araki with the information theoretic approach of Maurer for arbitrary $Q^2$ structures. We present both passive and actively secure (with abort) variants of our protocol. In all cases we require less communication channels than Maurer's protocol, at the expense of requiring pre-shared secret keys for Pseudo-Random Functions (PRFs). By shedding light on the theoretical underpinnings of the recent protocol of Araki et al. we hope that our work may result in future highly communication-efficient protocols for other access structures.

Category / Keywords: cryptographic protocols /