IACR News item: 11 April 2016
Houda Ferradi, Rémi Géraud, Diana Maimut, , David Naccache, David Pointcheval
ePrint Report
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 doesnt 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.
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