A FAIR PERFECT CONCURRENT SIGNATURE SCHEME

摘要

As we know, the concept of concurrent signatures was introduced by Chen et al.in Eurocrypt 2004 which allows two entities to produce two signatures in such a way that, the signer of each signature is ambiguous from any third party's point of view until the release of a secret,known as the keystone.Once the keystone is released,both signatures become binding to their respective signers concurrently.Because of the concurrent signature has many advantages than any other signatures,it contributes a novel approach for the traditional problem of fair exchange of signatures.However,in the previous concurrent signature schemes, the roles of participants are not equal,one party, which is called initial signer,needs to create the keystone fix and send the first ambiguous signature, the other party, which is called matching signer,responds to this initial signer by creating another ambiguous signature with the same keystone fix.This work mode may cause some unfairness.In this paper,we improve the Zhang's scheme and construct a novel scheme in which the two participants have equal positions, that means the keystones in our scheme are published by two signers,respectively.So our protocol can reach true fairness.