Reducing Communication Channels in MPC

In both information-theoretic and computationally-secure MultiParty Computation (MPC) protocols the parties are usually assumed to be connected by a complete network of secure or authenticated channels, respectively. Taking inspiration from a recent, highly efficient, threeparty honest-majority computationally-secure MPC protocol of Araki et al., we show how to perform the most costly part of a computationally secure MPC protocol for an arbitrary Q2 access structure over an incomplete network. We present both passive and actively secure (with abort) variants of our protocol. In all cases we require fewer communication channels for secure multiplication than Maurer’s “MPC-Made-Simple” protocol, at the expense of requiring pre-shared secret keys for PseudoRandom Functions (PRFs).