Efficient two-party SM2 signing protocol based on secret sharing

The digital signature is widely used in practice to verify a user’s identity and ensure data integrity for applications such as e-commerce and data exchange. The safe storage and reasonable use of the private key ensure the robustness of the cryptographic system. However, the private key stored in a single device faces the risk of invalidation due to theft or abuse. Moreover, the concentration of signature power inhibits their potential application in multi-user settings. Cooperative signature with the deployment of distributed key is a practical way to reduce the damage caused by key exposures. However, existing schemes of SM2 generally suffer from high computing overhead and exponential extension. In this paper, we present a new two-party SM2 protocol leveraging the Beaver’s multiplication that requires lower computational cost than previous two-party SM2 signing protocols. The proposed protocol is proven secure, as long as the standard SM2 signature scheme is secure. We implement our protocol in C to demonstrate that the proposed protocol has practical application prospects due to its efficiency advantage.