Implementing regular cash with blind fixed-value electronic coins

We propose a generic framework for the development of an off-line peer-to-peer electronic payment system with fixed-value electronic coins. The proposed scheme simulates the issuance, circulation and characteristics of conventional cash and satisfies important security, privacy and usability requirements, offering a comparative advantage over other existing solutions. We exploit the strong security characteristics of a typical tamperproof device such as a smart card, and the trust services provided by a Public Key Infrastructure. The electronic coins are fixed, signed data structures that may be distributed, stored and processed by external applications only in their blind (encrypted) form. Non-divisibility is counterbalanced by the low complexity of the proposed solution, which enables the efficient exchange of multiple coins per transaction.