The Research On Electronic Cash System With Multiple Banks Based On Group Signature Schemes

With the rapid development of electronic commerce, great changes of payment are taking place in recent years. The modern payment tool--electronic cash emerges as the times require and develops quickly. Therefore, it brings forward higher requirement on the modern payment systems. But now there are many difficult problems in the research of electronic cash system to be solved, such as membership revocation, transferability, divisibility, multiple banks and so on. As a branch of cryptography, the group signature offers the ability to hide interior structure of the organizing. So the scheme can be widely used in many domains. For example, we may use it for electronic government affair and electronic commerce, such as electronic voting, electronic bidding, electronic cash system, identity escrow etc.This paper defines an electronic cash system of multiple banks based on the group signature. Aiming at the existent problems of the group signature and electronic cash, we first design a new group signature with member revocation and then establish a new electronic cash system of multiple banks with more functions.As there are some deficiencies in all existent secure group signature scheme and member revocation, we first provide a new membership revocation method in this paper. In this new scheme, the size of public key only depends on the number of members in the group, and will not increase very rapidly along with the increment of number of revoked members. It needs only a multiplication or division operation to update the public key for the group manager to add or exclude a group member. The signing and verifying procedures are simpler than previous ones. The security of the new scheme is proved.Secondly, we present a fair off-line electronic cash system with multiple banks based on the improved group signature scheme introduced above. This model provides the functions of preventing customers from juggling the sum of electronic cash, member revocation, finding double-spending, and preventing criminal activities such as blackmailing, money laundering, and illegal purchases, revocable anonymity for customers.Finally, A practical cash system with multiple banks is implemented based on JBuilder and Oracle database.