Paper 2025/264

Dazzle: Improved Adaptive Threshold Signatures from DDH

Yanbo Chen, University of Ottawa
Abstract

The adaptive security of threshold signatures considers an adversary that adaptively corrupts users to learn their secret key shares and states. Crites, Komlo, and Maller (Crypto 2023) proposed Sparkle, the first threshold signature scheme in the pairing-free discrete-log setting to be proved adaptively secure. However, its proof of full adaptive security requires the algebraic group model (AGM) and is based on an interactive assumption. Bacho, Loss, Tessaro, Wagner, and Zhu (Eurocrypt 2024) proposed Twinkle, whose full adaptive security can be based on the standard DDH assumption only. We propose Dazzle and Dazzle-T, adaptively secure threshold signature schemes based on DDH without the AGM, the same assumption and model as Twinkle. Our schemes improve upon Twinkle in signature size, round complexity, and/or security tightness. In particular, Dazzle and Dazzle-T both have signatures that are shorter than Twinkle by one group element. Regarding the round complexity and tightness, Twinkle is three-round and non-tight. Our Dazzle is two-round and has the same security loss as Twinkle, while Dazzle-T is three-round and fully tight. We achieve our improvements by optimizing the underlying single-party signature scheme and showing that the single-party scheme can be transformed to a threshold scheme by a simpler transformation than that of Twinkle.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
Published by the IACR in PKC 2025
Keywords
Threshold SignaturesAdaptive SecurityPairing-FreeTightness
Contact author(s)
ychen918 @ uottawa ca
History
2025-02-18: approved
2025-02-18: received
See all versions
Short URL
https://ia.cr/2025/264
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2025/264,
      author = {Yanbo Chen},
      title = {Dazzle: Improved Adaptive Threshold Signatures from {DDH}},
      howpublished = {Cryptology {ePrint} Archive, Paper 2025/264},
      year = {2025},
      url = {https://eprint.iacr.org/2025/264}
}
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