An efficient contract signing protocol using the aggregate signature scheme to protect signers' privacy and promote reliability

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.

[1]  Markus Stadler,et al.  Publicly Verifiable Secret Sharing , 1996, EUROCRYPT.

[2]  Markus Jakobsson,et al.  Abuse-Free Optimistic Contract Signing , 1999, CRYPTO.

[3]  Manuel Blum,et al.  How to exchange (secret) keys , 1983, TOCS.

[4]  Colin Boyd,et al.  Off-Line Fair Payment Protocols Using Convertible Signatures , 1998, ASIACRYPT.

[5]  Kazuo Ohta,et al.  How to simultaneously exchange secrets by general assumptions , 1994, CCS '94.

[6]  Robert H. Deng,et al.  Practical protocols for certified electronic mail , 1996, Journal of Network and Systems Management.

[7]  Dieter Gollmann,et al.  A fair non-repudiation protocol , 1996, Proceedings 1996 IEEE Symposium on Security and Privacy.

[8]  Liqun Chen,et al.  Efficient Fair Exchange with Verifiable Confirmation of Signatures , 1998, ASIACRYPT.

[9]  Robert H. Deng,et al.  Efficient and practical fair exchange protocols with off-line TTP , 1998, Proceedings. 1998 IEEE Symposium on Security and Privacy (Cat. No.98CB36186).

[10]  Michael K. Reiter,et al.  Fair Exchange with a Semi-Trusted Third Party (extended abstract) , 1997, CCS.

[11]  Dan Boneh,et al.  Advances in Cryptology - CRYPTO 2003 , 2003, Lecture Notes in Computer Science.

[12]  Dieter Gollmann,et al.  An efficient non-repudiation protocol , 1997, Proceedings 10th Computer Security Foundations Workshop.

[13]  Hovav Shacham,et al.  Aggregate and Verifiably Encrypted Signatures from Bilinear Maps , 2003, EUROCRYPT.

[14]  Li Gong,et al.  Increasing Availability and Security of an Authentication Service , 1993, IEEE J. Sel. Areas Commun..

[15]  Oded Goldreich,et al.  A randomized protocol for signing contracts , 1985, CACM.

[16]  N. Asokan,et al.  Optimistic fair exchange of digital signatures , 1998, IEEE Journal on Selected Areas in Communications.