Behind the user interface, your computer actually chooses the serial numbers of the electronic coins based on a random seed. This way, when the bank receives from the shop the coins you spend, it cannot recognize them as coming from any particular withdrawal, because they were hidden in envelopes during withdrawal. And thus the bank cannot know when or where you shop or what you buy. The serial number of each signed coin is unique, allowing the bank to be sure it never accepts the same coin twice. In case you wish to identify the recipient of any of your payments, you can also reveal the serial number and prove that you formed it.
Security is fundamental to electronic cash.
The cryptographic coding protecting every 5 cent ecash payment is the same as that routinely relied upon for authenticating requests to move huge sums between banks and even for national security. Replacing paper and coins with ecash would make life much harder for criminals. Paper notes, briefcases full of which can be received without leaving any record, allow money laundering and tax evasion today. With ecash, however, all the amounts each person receives are known to their bank. Early, competing, and future systems Customers of Mark Twain Bank will have to fill out an application form that is available over the Internet, mail or fax it in, and receive a password by mail.