OptiVersa-ECDSA: Fast Threshold-ECDSA With Cheater Identification for Blockchains

Threshold-ECDSA is widely used to secure blockchain transactions on-chain or inter-chain thus their online performance is of great importance. The first practical thresholdECDSA was proposed by Gennaro and Goldfeder (CCS'18), based on which, Canetti et al. (CCS'20) built a threshold-ECDSA with cheater identification mechanism (CIM) and fast online signing. However, Canetti et al.'s protocol came with much more communication and computation burden and cannot apply to timely transactions. In this paper, we propose a performanceoptimized and versatile threshold-ECDSA (OptiVersa-ECDSA) with efficient CIM and fast online signing. We propose novel tools named “verifiable secret-product sharing (VSPS)” and batch VSPS, which is tailored for threshold-ECDSA. Security analysis shows that OptiVersa-ECDSA is secure against malicious adversaries in the dishonest majority model. The performance analysis shows that OptiVersa-ECDSA has 35%-65% bandwidth and runtime improvement (in particular, 99% for the CIM module), compared to Canetti et al. (CCS'20). These demonstrate that OptiVersa-ECDSA is a practical solution to secure the blockchain transactions.