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The electronic cash was introduced by Chaum in 1982 and now many e-cash systems have been proposed in order to mimic the fiat currency. Bitcoin provides us with an attractive way to construct a decentralized e-cash system. Ideally, we would like to make the system more practical, for example, the users can be able to transfer coins between each other multiple times and they can also withdraw arbitrary amount of coins rather than one or the predefined number, so that in the spend protocol the user can spend any amount of valid coins. In this paper, we propose a provably secure and more practical e-cash system. Firstly, it can provide the anonymous transfer of coins between users, so that the merchant can spend the received coins further; secondly, the user can withdraw arbitrary amount of coins rather than the one or predefined number; thirdly, during the transfer of coins, the coins have a fixed size; finally, the fair exchange between the users can also be achieved. |
