Card-based systems

Typically, a card-based e-money system is an electronic payment system based on a tamper-proof device, with the properties of being pseudo-anonymous, offline, and non-circulating. The term non-circulating refers to the fact that the monetary value once paid cannot be reused offline (by the payee of the first transaction) and must be redeemed. Being an offline system, it requires tamper-proof smartcards holding monetary values (for making payments), as well as tamper-proof devices for accepting payments. The devices for accepting payments require even higher level of protection as they may contain certain global cryptographic keys.

The e-money system outlined in Sections 2 and 3 is a network-based, online payment system. In this section we show how that system can be combined with this card-based system to offer additional services and functionality, i.e., VarietyCash. For example, the combined system allows transfer of monetary value from one system to another and vice versa. The advantages of one system can then be used in the other. Fortunately, these transfer protocols can be built at a high level, on top of the two systems.