How do Mondex smartcards work?
The exact technical specifications for Mondex electronic cash cards does not appear to be publicly available. However, the general security mechanisms for the Mondex card are available. Mondex uses public-key cryptography, and digital signatures, to authenticate transactions (Mondex, 1998). Each card, whether it be a merchant card or a consumer, has an embedded public key which can be used to digitally “sign” a transaction. This solves the problem of authentication of the merchant, and repudiation by the consumer. Figure 1 – Mondex consumer-merchant transaction The exact key size, or encryption algorithm, is not known. Presumably the key-size would be very low, so as to allow its export outside of the United States, and to allow its importation by encryption unfriendly nations such as France. The initial Mondex cards will have 16kb of ROM, and 8kb of re-writeable EEPROM for data storage (Mondex, 1998). Mondex cards will contain three logs, to track past transactions, pending transactio
