A new untraceable off-line electronic cash system

Digital content transactions through e-commerce will grow tremendously in the coming years. In this respect, well-designed electronic payment schemes and high-quality digital contents are two critical factors. Untraceable electronic cash schemes make it possible for customers to pay the e-cash to the merchants through communication networks under privacy protection. Therefore, there is a need to invent new electronic payment protocols with strong cryptographic algorithms that will eventually replace present day paper-based cash schemes. There have been two types of electronic cash schemes, namely on-line and off-line. In general off-line schemes are more efficient than on-line ones. The two fundamental issues with any off-line electronic cash scheme have been the detection of double-spending and provision of anonymity. This paper proposes a new untraceable off-line electronic cash scheme which can maintain anonymity and double spender detection and possesses strong fraud control capabilities. Moreover, the proposed scheme attaches expiration date to coins so that the banking system can manage its databases more efficiently. The scheme is based on cryptographic techniques such as ElGamal and blind signatures. The coins produced by the scheme can be transferred through computer networks into storage devices and vice versa so that portability is assured.