Group Blind Signature And Its Application To Multi-Bank E-cash System

With the development of Internet, electronic commerce has attracted more and more attentions as a new commerce mode. Many companies have already offered their strategies to solve this problem. Many governments and international organizations have also provided helpful rules and strategies. It seems that electronic commerce has become the biggest spoondrift of the information technology river.Electronic payment systems are significant for electronic commerce. Electronic cash is a very important electronic payment system. In this thesis, we pay our big attention to how to use some modern cryptographic technologies ,such as Group Digital Signature, Blind Digital Signature, Group Blind Digital Signature to construct a new electronic cash system. The whole thesis was composed of two parts: First, study on a new cryptographic construct called Group Blind Digital Signature; Second, study on multi-bank electronic cash system.1) Recently, group signatures, blind signatures and their combination result called group blind signatures which have been widely used in political area, military area and commerce area have been becoming the hot topics of modern cryptographic technology. For example, they have already been used in electronic election, electronic voting and electronic cash. This thesis first introduced the famous group blind digital signature--Lys98, and then proved that this original scheme was not safe enough to resist a coalition-attack, in the end, provided two modified schemes of the original scheme to avoid the attack.2) Before 1998, all of the e-cash systems were based on a "single model" which means only one bank has the ability to issue e-cash, shops and their users have to use the same bank. But as we know, multi-bank e-cash system where every bank can issue e-cash, shops and their users can use different banks is more practical than the single-bank one. So in the second part of this thesis we used our modified group blind digital signature to construct an off-line and anonymity-revoking multi-bank e-cash system.