The Research On Divisible E-cash System And Its Implementation Technique

Because of its excellent properties of off-line transaction,keeping user anonymous, convenience and flexibility,and being able to effectively prevent repudiation of payment and overdrawing with evil intentions,e-cash has become one of the most important electronic payment modes.And it already has become the future trend of development of electronic money.Divisibility is one of the most basic and natural properties of currency of any kind.A Divisible e-cash can either be used as an entirety or be divided into smaller parts.This way,the users could reduce the numbers of withdraw.What's more, not only the network traffic will be lighter,but also the system will be more efficiency. Therefore,the divisibility of the e-cash has always been an important and hot point of this field.There is a long way to go for e-cash to being putted into practice.The detection of duplication of payments and over paid,will made the protocols of e-cash complicated, the computational complexity of the protocols increased,and the efficiency of implementation declined.We can use the trusted third party(TTP) to track the illegal users to avoid making the protocol complicated;however,the TTP poses a threat to the user's anonymity,and will lead to additional costs of the system.Usually,different parts of a divisible e-cash have relevance which is a potential threat of leaking the user's privacy.This paper commits itself to construct divisible e-cash Systems with excellent properties and high efficiency,and explore the new clue of thoughts of divisible e-cash system.Firstly,we analyzed and summarized the key implementation techniques of e-cash systems,including the techniques of divisible e-cash systems,and compared the related techniques.Secondly,we do a lot to explore good clue of thoughts and new advances in technology of divisible e-cash system,and propose two divisible e-cash schemes.The first one has the full-unlinkability property by reason of using many effective zero-knowledge proofs.In another words,a user cannot leak any of his privacy,including the nodes information of the cash he was using.Meanwhile,there is no a TTP in the scheme.The second one is a useful and valid attempt to improve the e-cash system efficiency.In this scheme,we take advantage of probabilistic algorithm and the boundedness of the one-way accumulator instead of the traditional cut-choose algorithm. As a result,the scheme is proven more efficient,no TTP,and unlinkability.Finally,we point some open problems of electronic cash and prospect the future research of e-cash.