An online, transferable e-cash payment system

Abstract

Most electronic cash (e-cash) based payment systems that have been proposed do not possess the property of transferability. Transferability in an e-cash based system means that when a payee receives an electronic coin in a transaction he may spend it without depositing the coin first and getting a new coin issued from a bank. Usually electronic coins that are transferred in a transaction have a lifetime of the transaction itself. In this paper, we propose a payment system where coins can be transferred over multiple hands, spread over various transactions, similar to physical cash. Detection or prevention of double spending of coins is a critical issue in online e-cash payment systems. In our system the verification is distributed across multiple entities as opposed to the case of a coin-issuing entity or a central bank alone being responsible for the verification. A resolution mechanism for handling disputes is also presented. The proposed system provides guarantees of anonymity, fairness and transferability.