Mithril: Stake-based Threshold Multisignatures

Pyrros Chaidos; Aggelos Kiayias

Paper 2021/916

Mithril: Stake-based Threshold Multisignatures

Pyrros Chaidos, National and Kapodistrian University of Athens

Aggelos Kiayias, University of Edinburgh

Abstract

Stake-based multiparty cryptographic primitives operate in a setting where participants are associated with their stake, security is argued against an adversary that is bounded by the total stake it possesses —as opposed to number of parties— and we are interested in scalability, i.e., the complexity of critical operations depends only logarithmically in the number of participants (who are assumed to be numerous). In this work we put forth a new stake-based primitive, stake-based threshold multisignatures (STM, or “Mithril” signatures), which allows the aggregation of individual signatures into a compact multisignature provided the stake that supports a given message exceeds a stake threshold. This is achieved by having for each message a pseudorandomly sampled subset of participants eligible to issue an individual signature; this ensures the scalability of signing, aggregation and verification. We formalize the primitive in the universal composition setting and propose efficient constructions for STMs. We also showcase that STMs are eminently useful in the cryptocurrency setting by providing two applications: (i) stakeholder decision-making for Proof of Work (PoW) blockchains, specifically, Bitcoin, and (ii) fast bootstrapping for Proof of Stake (PoS) blockchains.

Note: Updated aggregate verification.

Metadata

Available format(s): PDF
Category: Cryptographic protocols
Publication info: Preprint.
Keywords: digital signatures zero knowledge blockchains
Contact author(s): p chaidos @ di uoa gr
History: 2022-09-26: last of 5 revisions; 2021-07-08: received; See all versions
Short URL: https://ia.cr/2021/916
License: CC BY

BibTeX

@misc{cryptoeprint:2021/916,
      author = {Pyrros Chaidos and Aggelos Kiayias},
      title = {Mithril: Stake-based Threshold Multisignatures},
      howpublished = {Cryptology ePrint Archive, Paper 2021/916},
      year = {2021},
      note = {\url{https://eprint.iacr.org/2021/916}},
      url = {https://eprint.iacr.org/2021/916}
}