Abstract Threshold signatures are essential for fault-tolerant applications among groups of users, such as in blockchain transactions. SM2 is a digital signature standard in China and ISO, yet its threshold variant is less developed compared to international alternatives such as ECDSA. Specifically, modern threshold signatures offer identifiable abort (ID-abort) and non-interactive online signing, but these features make threshold-SM2 costly, limiting its real-world application. In this paper, we introduce a fast threshold-SM2 with ID-abort and non-interactive online signing. We design a technology for ID-abort by checking hard-to-verify pseudononces based on their mappings in a group. By putting the message-independent computations to a presigning phase, we achieve a non-interactive online signing. We prove that our threshold-SM2 is secure in the dishonest majority model and implement it using Golang. Theoretical analysis and experimental results demonstrate that our threshold-SM2 provides rich functionalities with good performance, significantly reducing computational and communication costs compared to the state-of-the-art threshold-SM2 by Liang and Chen (FCS’ 24).

Abstract Atomic Cross-Chain Swap (ACCS) is one important topic in cryptocurrency, where users can securely and trustlessly exchange assets between two different blockchains. However, most known ACCS schemes assume specific scripting functionalities of the underlying blockchains, such as Hash Time Locked Contracts (HTLC). In addition, these schemes are typically only applicable to certain digital signature schemes, like Schnorr or Elliptic Curve Digital Signature Algorithm (ECDSA) signatures. In this paper, we propose a generic ACCS scheme, independent from the underlying blockchains. To the best of our knowledge, this is the first solution of this kind. Our results are as follows. First, we define a formal system model of ACCS. Next, we present a generic ACCS scheme meets our model. This scheme admits atomicity in cross-chain swaps without the need for a Trusted Third Party (TTP) and protects users’ privacy. Finally, by using the Non-Interactive Zero-Knowledge (NIZK) proof protocol as a tool, we instantiate our generic scheme for Elliptic Curve Discrete Logarithm Problem-based (ECDLP-based) signatures. In addition, we implement our scheme, and the experimental results show that our protocol outperforms the existing ACCS schemes, such as the HTLC-based schemes.