Improved Cryptographic protocol for digital coin exchange

摘要

In this paper we describe a serious vulnerability of the well-known protocol for exchange of anonymous currency by David Chaum. The weakness of the system consists in the possibility of spending an electronic coin more than once, which can lead to the serious frauds by both the client and the seller. What is more, the system cannot determine the right number of transactions, which were made and the bank is not able to charge the real abuser.