Unconditional Communication-Efficient MPC via Hall's Marriage Theorem

The best known $n$ party unconditional multiparty computation protocols with an optimal corruption threshold communicates $O(n)$ field elements per gate. This has been the case even in the semi-honest setting despite over a decade of research on communication complexity in this setting. Going to the slightly sub-optimal corruption setting, the work of Damgard, Ishai, and Kroigaard (EUROCRYPT 2010) provided the first protocol for a single circuit achieving communication complexity of $O(\log|C|)$ elements per gate. While a number of works have improved upon this result, obtaining a protocol with $O(1)$ field elements per gate has been an open problem.

In this work, we construct the first unconditional multi-party computation protocol evaluating a single arithmetic circuit with amortized communication complexity of $O(1)$ elements per gate.