Dynamic-FROST: Schnorr Threshold Signatures with a Flexible Committee

Annalisa Cimatti; Francesco De Sclavis; Giuseppe Galano; Sara Giammusso; Michela Iezzi; Antonio Muci; Matteo Nardelli; Marco Pedicini

Paper 2024/896

Dynamic-FROST: Schnorr Threshold Signatures with a Flexible Committee

Annalisa Cimatti

, Roma Tre University

Francesco De Sclavis

, Bank of Italy

Giuseppe Galano

, Bank of Italy, University of Pisa

Sara Giammusso

, Bank of Italy

Michela Iezzi, Bank of Italy

Antonio Muci, Bank of Italy

Matteo Nardelli

, Bank of Italy

Marco Pedicini

, Roma Tre University

Abstract

Threshold signatures enable any subgroup of predefined cardinality $t$ out of a committee of $n$ participants to generate a valid, aggregated signature. Although several $(t,n)$-threshold signature schemes exist, most of them assume that the threshold $t$ and the set of participants do not change over time. Practical applications of threshold signatures might benefit from the possibility of updating the threshold or the committee of participants. Examples of such applications are consensus algorithms and blockchain wallets. In this paper, we present Dynamic-FROST (D-FROST, for short) that combines FROST, a Schnorr threshold signature scheme, with CHURP, a dynamic proactive secret sharing scheme. The resulting protocol is the first Schnorr threshold signature scheme that accommodates changes in both the committee and the threshold value without relying on a trusted third party. Besides detailing the protocol, we present a proof of its security: as the original signing scheme, D-FROST preserves the property of Existential Unforgeability under Chosen-Message Attack.

Metadata

Available format(s): PDF
Category: Cryptographic protocols
Publication info: Preprint.
Keywords: Proactive secret sharing Threshold signatures Decentralization FROST CHURP
Contact author(s): ann cimatti @ stud uniroma3 it
francesco desclavis @ bancaditalia it
giuseppe galano2 @ bancaditalia it
sara giammusso @ bancaditalia it
michela iezzi @ bancaditalia it
antonio muci @ bancaditalia it
matteo nardelli @ bancaditalia it
marco pedicini @ uniroma3 it
History: 2024-06-06: approved; 2024-06-05: received; See all versions
Short URL: https://ia.cr/2024/896
License: CC BY-SA

BibTeX

@misc{cryptoeprint:2024/896,
      author = {Annalisa Cimatti and Francesco De Sclavis and Giuseppe Galano and Sara Giammusso and Michela Iezzi and Antonio Muci and Matteo Nardelli and Marco Pedicini},
      title = {Dynamic-{FROST}: Schnorr Threshold Signatures with a Flexible Committee},
      howpublished = {Cryptology ePrint Archive, Paper 2024/896},
      year = {2024},
      note = {\url{https://eprint.iacr.org/2024/896}},
      url = {https://eprint.iacr.org/2024/896}
}