An Efficient Contract Signing Protocol Using the Aggregate Signature Scheme to Protect Signers' Privacy and Promote Reliability

摘要

Contract signing conducted over the Internet arouses concerns of fairness. Two signing parties exchange their signatures in a fair manner, so that no party can gain an advantage over the other. This paper will discuss the security issues of signers' privacy and reliability of the system for the contract signing protocol. The trusted third party (TTP), responsible for maintaining the fairness in the protocol, cannot get useful information about the exchanged signatures by solving the dispute between two parties. The concept of semi-trusted third party (STTP) adopted from Franklin and Reiter's paper (in 1997) can be used to reach our goal. However, Franklin and Reiter's protocol uses an on-line third party and is inapplicable to the exchange of signatures. Hence, we propose an efficient contract signing protocol with off-line STTP using the aggregate signature proposed by Boneh and Gentry. Furthermore, the use of aggregate signature and bilinear pairings will effectually promote system reliability.