一个对eCash^(TM)改进的实用电子现金系统

An Practical Electronic Cash System——An Improvement on the eCash^(TM)

具有纸币的优点克服其不足是设计电子现金的总则之一 .作者发现广泛使用的 e Cash TM系统有两个缺陷 :(1)他人获得合法用户的电子现金可盗用 ;(2 )银行与用户之间发生电子现金是否被重复花费的争议时无法仲裁 .该文给出了一个具有 e Cash TM优点并克服了上述缺陷的实用系统 ,效率和复杂度与 e Cash TM基本相同 ,电子现金的形式是 { gx,hd(gx) } ,x为用户秘密 ,将来用之对支付信息进行签字 .

The future electronic cash should have all the advantages of notes and without the disadvantages of them. There are two flaws in the eCash TM system: (1) anyone who somehow observes the eCash TM Coins can spend them; (2)when the dispute about if one Coin has been double spent between Bank and a user takes place, it should be impossible for other person to arbitrate it. In spite of that eCash TM is still used today because paper notes inherently have these flaws. In this paper we give a novel method that can avoid the above flaws. The format of coins in our improvement is { g x , h(g x ) d } , where g is a multiple generator of a field, h is a secure hash function, d is issue bank's RSA secret key, and x is a random number generated by users during the applying session which is only known to the applier. During payment session, the user who holds a digital coin { g x , h(g x ) d } and the corresponding secret x computes a digital ElGamal signature on the payment information. For unknowing x anyone else who gets the coin {g x , h(g x ) d } can not spend it, and it is due to the x that the above flaws in the eCash TM system are avoided. In the eCash TM system another public key is needed in payment session for ciphering coins in order to keep the coins secret from other users, the public key is not needed in our improved system and the ciphering and deciphering computation is also saved So our improvement on the eCash TM is not inefficient or more complex than eCash TM .