Legally Fair Contract Signing Without Keystones

  • Houda Ferradi
  • Rémi Géraud
  • Diana Maimuț
  • David Naccache
  • David Pointcheval
Conference paper

DOI: 10.1007/978-3-319-39555-5_10

Volume 9696 of the book series Lecture Notes in Computer Science (LNCS)
Cite this paper as:
Ferradi H., Géraud R., Maimuț D., Naccache D., Pointcheval D. (2016) Legally Fair Contract Signing Without Keystones. In: Manulis M., Sadeghi AR., Schneider S. (eds) Applied Cryptography and Network Security. ACNS 2016. Lecture Notes in Computer Science, vol 9696. Springer, Cham

Abstract

In two-party computation, achieving both fairness and guaranteed output delivery is well known to be impossible. Despite this limitation, many approaches provide solutions of practical interest by weakening somewhat the fairness requirement. Such approaches fall roughly in three categories: “gradual release” schemes assume that the aggrieved party can eventually reconstruct the missing information; “optimistic schemes” assume a trusted third party arbitrator that can restore fairness in case of litigation; and “concurrent” or “legally fair” schemes in which a breach of fairness is compensated by the aggrieved party having a digitally signed cheque from the other party (called the keystone).

In this paper we describe and analyse a new contract signing paradigm that doesn’t require keystones to achieve legal fairness, and give a concrete construction based on Schnorr signatures which is compatible with standard Schnorr signatures and provably secure.

Copyright information

© Springer International Publishing Switzerland 2016

Authors and Affiliations

  • Houda Ferradi
    • 1
  • Rémi Géraud
    • 1
  • Diana Maimuț
    • 1
  • David Naccache
    • 1
  • David Pointcheval
    • 1
  1. 1.École Normale SupérieureParis Cedex 05France