Introduction to Cryptography with Coding Theory, 3rd Edition

16.2 A Digital Cash System

This section is not needed for the remaining sections of the chapter. It is included because it has some interesting ideas and it shows how hard it is to achieve the desired requirements of a digital currency.

We describe a system due to S. Brands [Brands]. The reader will surely notice that it is much more complicated than the centuries-old system of actual coins. This is because, as we mentioned previously, electronic objects can be reproduced at essentially no cost, in contrast to physical cash, which has usually been rather difficult to counterfeit. Therefore, steps are needed to catch electronic cash counterfeiters. But this means that something like a user’s signature needs to be attached to an electronic coin. ...