2PC-MPC: Emulating Two Party ECDSA in Large-Scale MPC

Abstract

Motivated by the need for a massively decentralized network concurrently servicing many clients, we present novel low-overhead UC-secure, publicly verifiable, threshold ECDSA protocols with identifiable abort.

The paper demonstrates reduction of message complexity from O(n²) to O(n) and computational complexity from O(n) to practically O(1) per party, where n represents the number of parties. The approach requires only a broadcast channel for communication, supporting use-cases like permissionless bridges and decentralized custody, where P2P channels between every pair of parties are infeasible.

We introduce the 2PC-MPC protocol — a two-party ECDSA protocol where the second party is fully emulated by a network of n parties, ensuring both a client and network threshold participate in signing while maintaining client complexity independent of network size.

Implementation Results: The signing phase completes in 1.23 seconds for 256 parties and 12.703 seconds for 1024 parties.