Mondex is a payment system in which currency is stored in smart cards. These smart cards are similar in shape and size to credit cards, and generally permit the storage of sums of money up to several hundred dollars. Money may be transferred from card to card arbitrarily many times and in any chosen amounts. There is no concern about coin sizes, as with traditional currency. The Mondex system also provides a limited amount of anonymity. The system carries with it one of the disadvantages of physical currency: if a Mondex card is lost, the money it contains is also lost. Transfers of funds from card to card are effected with any one of a range of intermediate hardware devices.
The Mondex system relies for its security on a combination of cryptography and tamper-resistant hardware. The protocol for transferring funds from one card to another, for instance, makes use of digital signatures (although Mondex has not yet divulged information about the algorithms employed). Additionally, the system assumes that users cannot tamper with cards, that is, access and alter the balances stored in their cards. The Mondex system is managed by a corporation known as Mondex International Ltd., with a number of associated national franchises. Pilots of the system have been initiated in numerous cities around the world.
For more information on Mondex, visit their web site at http://www.mondex.com.