An Efficient Threshold Scheme for Two-party ECDSA

An efficient two-party ECDSA threshold scheme is proposed to fix the problems of existing threshold ECDSA schemes, e.g., some signature protocols having too much computation overhead or too many interaction rounds, leading to low signature efficiency, and some signature protocols having OT (oblivious transfer) to replace the Paillier homomorphic encryption technology, increasing the communication cost by thousands of times. The scheme divides the signature private key into two parts to be kept by two parties respectively. Using the homomorphic encryption technology, each collaborative signature requires both users to participate in the signature process at the same time. In addition, the signature phase is divided into the offline precomputation phase and the online signature phase. Most of the computation is completed in advance in the offline precomputation phase. The online signature phase is efficient and fast, which improves the signature efficiency. The correctness analysis and security proof of the scheme are given, and the two ECDSA schemes proposed by Lindell and this current scheme are compared in terms of theoretical analysis. The results show that the scheme avoids the expensive homomorphic operation in the online signature phase and has the advantages of high signature efficiency, low communication cost, less interaction rounds and higher practicability.