Research On Implementation Of Transferable Of-Line Electronic Cash With Finite Circulation Period

The thesis aim at research on e-cash payment via Internet which is more secure and more convenient and more approaching physical cash in contrast with all of e-cash schemes already proposed. The thesis introduces some relevant theories, key technologies of e-cash protocols and summarizes the history, status quo, achievements of e-cash theory and the present progress of practical e-cash systems abroad. Applying both our partially restrictive blind signature protocol and restrictive blind signature protocol, the thesis also proposes a new efficient transferable off-line e-cash system with finite circulation period based on ellipse curve. Open protocol and withdrawal protocol and payment protocol and deposit protocol in the off-line electronic cash system are described detailedly. The security of the scheme on unforgeability, untraceability, no double spending is proved. At the same time the system is also extended to e-cash system with smart card. The transferability of off-line electronic cash is implemented based on smart card. Thus the security of the scheme is improved dramatically. As we apply partially restrictive blind signature protocol in this system and denomination of e-cash may be plaintext in the code of e-cash, the e-cash with various denominations can be issued only by a single secret key for the bank. At the same time, the size of payment transcript database of bank can be controlled in a rational range as the concept of validity duration for e-cash is introduced.