Off-line anonymous electronic money
In off-line electronic money the merchant does not need to interact with the bank before accepting a coin from the user. Instead he can collect multiple coins Spent by users and Deposit them later with the bank. In principle this could be done off-line, i.e. the the merchant could go to the bank with his storage media to exchange e-cash for cash. Nevertheless the merchant is guaranteed that the user's e-coin will either be accepted by the bank, or the bank will be able to identify and punish the cheating user. In this way a user is prevented from spending the same coin twice (double-spending). Off-line e-cash schemes also need to protect against cheating merchants, i.e. merchants that want to deposit a coin twice (and then blame the user).
In cryptography anonymous e-cash was introduced by David Chaum. He used blind signatures to achieve unlinkability between withdrawal and spend transactions.[1] In cryptography, e-cash usually refers to anonymous e-cash. Depending on the properties of the payment transactions, one distinguishes between on-line and off-line e-cash. The first off-line e-cash system was proposed by Chaum and Naor [2]. Like the first on-line scheme, it is based on RSA blind signatures.
Future evolution
The main focuses of digital cash development are 1) being able to use it through a wider range of hardware such as secured credit cards; and 2) linked bank accounts that would generally be used over an internet means, for exchange with a secure micropayment system such as in large corporations (PayPal).
Furthering network evolution in terms of the use of digital cash, a company named DigiCash is at the focus of creating an e-cash system that would allow issuers to sell electronic coins at some value. When they are purchased they come under someone’s own name and are stored on his computer or under his online identity. At all times, the e-cash is linked to the e-cash company and all transactions go through it, so the e-cash company secures anything that is purchased. Only the company knows your information and will properly direct purchases to your location.
Theoretical developments in the area of decentralized money are underway that may rival traditional, centralized money. Systems of accounting such as Altruistic Economics are emerging that are entirely electronic, and can be more efficient and more realistic because they do not assume a zero-sum transaction model.
