Publication Type

Conference Proceeding Article

Version

acceptedVersion

Publication Date

5-2025

Abstract

Threshold signatures, especially ECDSA, enhance key protection by addressing the single-point-of-failure issue. Threshold signing can be divided into offline and online phases, based on whether the message is required. Schemes with low-cost online phases are referred to as “online-friendly”. Another critical aspect of threshold ECDSA for real-world applications is robustness, which guarantees the successful completion of each signing execution whenever a threshold number t of semi-honest participants is met, even in the presence of misbehaving signatories. The state-of-the-art online-friendly threshold ECDSA with-out robustness was developed by Doerner et al. in S&P'24, requiring only three rounds. Recent work by Wong et al. in NDSS'23 (WMY+23) and NDSS'24 (WMC24) achieves robustness but demands additional communication rounds (7 and 4, respectively) or incurs costly operations in the online phase, such as computations over a homomorphic encryption scheme. This paper presents the first three-round threshold ECDSA scheme with both robustness and an online-friendly design. The online phase of our scheme relies solely on several elliptic-curve group operations, which are 2 to 3 orders of magnitude less computationally intensive than those based on linearly homomorphic encryption schemes. We implement our protocol and conduct a comprehensive comparison with WMY+23 and WMC24. Benchmark results show that the online phase of our scheme is 2.5x faster than that of WMY+23 and hundreds of times faster than that of WMC24. Lastly, we demonstrate that our techniques can be extended to construct an online-friendly and robust three-round threshold BBS + scheme.

Discipline

Information Security

Research Areas

Information Systems and Management

Areas of Excellence

Digital transformation

Publication

Proceedings of the 2025 IEEE Symposium on Security and Privacy (SP), San Francisco, CA, May 12-15

First Page

203

Last Page

221

ISBN

9798331522360

Identifier

10.1109/sp61157.2025.00115

Publisher

IEEE Computer Society

City or Country

Los Alamitos, CA

Additional URL

https://doi.org/10.1109/sp61157.2025.00115

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