Internet cash - a realistic ideal for electronic money

An electronic money service based on NTT's ideal electronic cash scheme was started in September 1998. This scheme is ideal because it satisfies all the requirements for electronic money such as: supporting transfers, protecting user privacy, preventing illegal use, and tracing malicious users. NTT developed the Internet Cash system, which satisfies all the features of NTT's electronic cash scheme and applied it to a real service. This paper describes the Internet Cash system and explains solutions to development issues such as: preventing duplicate use, resuming processing after line disconnections, inspecting unusable IC cards, and estimating the amount remaining in a broken IC card.