Protocol for irreversible off-line transactions in anonymous electronic currency exchange

摘要

This paper presents an improvement to the wellknown protocol by David Chaum for anonymous currency exchange.We showits vulnerability to serious frauds by both the client and the seller, after an electronic coin is spent at least twice. In this case, the system cannot successfully determine howmany times the client spent the coin and howmany times the seller faked the transaction. Therefore, the bank is not able to charge the real abuser. This limitation leads to the conclusion that the original system cannot be securely used for irreversible off-line transactions. In this paper, we show the gist of the problem and propose an improved system based on its original off-line version that allows this vulnerability to be overcome.