## Cryptology ePrint Archive: Report 2019/646

Communication-Efficient Unconditional MPC with Guaranteed Output Delivery

Vipul Goyal and Yanyi Liu and Yifan Song

Abstract: We study the communication complexity of unconditionally secure MPC with guaranteed output delivery over point-to-point channels for corruption threshold $t < n/3$. We ask the question: “is it possible to construct MPC in this setting s.t. the communication complexity per multiplication gate is linear in the number of parties?” While a number of works have focused on reducing the communication complexity in this setting, the answer to the above question has remained elusive for over a decade. We resolve the above question in the affirmative by providing an MPC with communication complexity $O(Cn\kappa + n^3\kappa)$ where $\kappa$ is the size of an element in the field, $C$ is the size of the (arithmetic) circuit, and, $n$ is the number of parties. This represents a strict improvement over the previously best known communication complexity of $O(Cn\kappa+D_Mn^2\kappa+ n^3\kappa)$ where $D_M$ is the multiplicative depth of the circuit. To obtain this result, we introduce a novel technique called 4-consistent tuples of sharings which we believe to be of independent interest.

Category / Keywords: cryptographic protocols / Multiparty Computation, Information-theoretic Cryptography, Communication Complexity

Original Publication (with minor differences): IACR-CRYPTO-2019