Research On Multi-bank E-cash Payment Scheme Based On The Third Trusted Part

As a new type of payment, e-cash maintains all characters of traditional cash, and it is stored with digital form which can make the use more convenient. So it has become a new hotspot for research all over the world. Academicians design a series of e-cash model in order to ensure the trade's safety, impartiality, anonymity, non repudiation, and fairness.This paper introduces knowledge of cryptology and digital signature which are the base of the e-cash, and studies the e-cash scheme from two aspects:analyses the security of the scheme by Wang Daxing and then designs a new scheme. Main contents are as follows:Firstly, the paper gives a definition of e-cash, and describes e-cash's basic characters, and introduces its applications,and analyses the research on theoretic.Secondly, the paper introduces the basic knowledge which is related to e-cash, including the theory of Public key cryptosystem and digital signature, and gives basic models of digital signature based on RSA and discrete logarithm, and introduces the knowledge of blind signature and group signature and signature of knowledge.Thirdly, the paper analyses the anonymity-revocable divisible multi-bank e-cash payment scheme by Wang Daxing, and indicates that anyone can forge a certificate of a member in the group without being pursued. So that e-cash can be forged optionally. The research indicates that this scheme is not anonymity-revocable and is not divisible. As a result of the insecurity, this scheme is not applied in use.Finally, a new Multi-bank E-Cash payment scheme based on the third trusted part is designed. The analysis indicates that this scheme can prevent the forging of the e-cash, and is anonymity-revocable. It can prevent the seller depositing the same e-cash twice, and open the identity of the issuer bank. Therefore, this scheme can be applied in use.