International Association for Cryptologic Research

International Association
for Cryptologic Research


Snowblind: A Threshold Blind Signature in Pairing-Free Groups

Elizabeth Crites , University of Edinburgh
Chelsea Komlo , University of Waterloo & Zcash Foundation
Mary Maller , Ethereum Foundation & PQShield
Stefano Tessaro , University of Washington
Chenzhi Zhu , University of Washington
DOI: 10.1007/978-3-031-38557-5_23 (login may be required)
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Presentation: Slides
Conference: CRYPTO 2023
Abstract: Both threshold and blind signatures have, individually, received a considerable amount of attention. However little is known about their combination, i.e., a threshold signature which is also blind, in that no coalition of signers learns anything about the message being signed or the signature being produced. Several applications of blind signatures (e.g., anonymous tokens) would benefit from distributed signing as a means to increase trust in the service and hence reduce the risks of key compromise. This paper builds the first blind threshold signatures in pairing-free groups. Our main contribution is a construction that transforms an underlying blind non-threshold signature scheme with a suitable structure into a threshold scheme, preserving its blindness. The resulting signing protocol proceeds in three rounds, and produces signatures consisting of one group element and two scalars. The underlying non-threshold blind signature schemes are of independent interest, and improve upon the current state of the art (Tessaro and Zhu, EUROCRYPT ’22) with shorter signatures (three elements, instead of four) and simpler proofs of security. All of our schemes are proved secure in the Random Oracle and Algebraic Group Models, assuming the hardness of the discrete logarithm problem.
  title={Snowblind: A Threshold Blind Signature in Pairing-Free Groups},
  author={Elizabeth Crites and Chelsea Komlo and Mary Maller and Stefano Tessaro and Chenzhi Zhu},