Breaking and repairing optimistic fair exchange from PODC 2003

Yevgeniy Dodis, Leonid Reyzin

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

In PODC 2003, Park, Chong, Siegel and Ray proposed an optimistic protocol for fair exchange, based on RSA signatures. We show that their protocol is totally breakable already in the registration phase: the honest-but-curious arbitrator can easily determine the signer's secret key. On a positive note, the authors of informally introduced a connection between fair exchange and "sequential two-party multisignature schemes" (which we call two-signatures), but used an insecure two-signature scheme in their actual construction. Nonetheless, we show that this connection can be properly formalized to imply provably secure fair exchange protocols. By utilizing the state-of-the-art non-interactive two-signature of Boldyreva, we obtain an efficient and provably secure (in the random oracle model) fair exchange protocol, which is based on GDH signatures. Of independent interest, we introduce a unified model for non-interactive fair exchange protocols, which results in a new primitive we call verifiably committed signatures. Verifiably committed signatures generalize (non-interactive) verifiably encrypted signatures and two-signatures, both of which are sufficient for fair exchange.

Original languageEnglish (US)
Title of host publicationDRM 2003
Subtitle of host publicationProceedings of the Third ACM Workshop on Digital Rights Management
PublisherAssociation for Computing Machinery (ACM)
Pages47-54
Number of pages8
ISBN (Print)1581137869, 9781581137866
DOIs
StatePublished - 2003
EventDRM 2003: Proceedings of the Third ACM Workshop on Digital Rights Management - Washington, DC, United States
Duration: Oct 27 2003Oct 27 2003

Publication series

NameDRM 2003: Proceedings of the Third ACM Workshop on Digital Rights Management

Other

OtherDRM 2003: Proceedings of the Third ACM Workshop on Digital Rights Management
CountryUnited States
CityWashington, DC
Period10/27/0310/27/03

Keywords

  • Digital signatures
  • Fair exchange
  • Multisignatures
  • Verifiably committed signatures
  • Verifiably encrypted signatures

ASJC Scopus subject areas

  • Engineering(all)

Cite this

Dodis, Y., & Reyzin, L. (2003). Breaking and repairing optimistic fair exchange from PODC 2003. In DRM 2003: Proceedings of the Third ACM Workshop on Digital Rights Management (pp. 47-54). (DRM 2003: Proceedings of the Third ACM Workshop on Digital Rights Management). Association for Computing Machinery (ACM). https://doi.org/10.1145/947380.947387