The Research of Concurrent Signature Scheme with Security Enhancement and Its Application on Fair Exchange Protocol

• Main Authors: Chao-Chuan Chen, 陳昭權
• Other Authors: Chih-Hung Wang
• Format: Others
• Language: en_US
• Online Access: http://ndltd.ncl.edu.tw/handle/62473043777633793044

碩士 === 國立嘉義大學 === 資訊工程學系研究所 === 100 === With the rapid development of Internet, E-Commerce has attracted more and more attention. How to ensure the security and fairness of transaction via the Internet is a critical issue. Briefly, a fair exchange is defined that the two involved parties, after the fair exchange succeeds, can obtain their wanted valuable goods or neither of them can obtain useful information. In 2004, Chen et al. proposed a new kind of signature called concurrent signature (CS). Concurrent signature, which does not need the assistance of TTP and has few message interactions, can provide an alternative approach to solve the fair exchange problem. During the exchange protocol, the signatures generated by the two involved parties are ambiguous with respect to the identity of the signers before an extra piece of information (i.e. keystone) is released by one party. However, the party who controls the keystone has a degree of advantage over the other. It is failed to achieve full fairness. In this thesis, we point out the design drawbacks of the previous literatures which suffer from the message substitute attack. Therefore, we propose an improved scheme that can satisfy the property of accountability. Moreover, an extended scheme to the identity-based concurrent signature with improved accountability is also proposed. A new concept to achieve the full fairness of concurrent signature scheme is presented to provide an efficient conversion mechanism. Similar to the traditional fair exchange, a trusted third party who acts as an arbiter to solve the dispute between the two parties is involved in our new designed model.