A new off-line electronic cash scheme for bank delegation

Due to the high-speed, low-cost ubiquity of the internet and wireless networks access, the electronic commerce has attracted extensive attention from both academia and industry in the past decade. Electronic cash(e-cash) is a popular billing mechanism for electronic transactions since it can fully protect the anonymity and identity privacy of customers in various electronic transactions. To support withdrawing and storing money from all levels of the bank for the customers in the real world, in this paper, we propose a proxy blind signature scheme and an e-cash scheme based on the new proxy blind signature scheme. The proxy blind signature scheme is proved secure in the Random Oracle Model under the chosen-target computational Diffie-Hellman assumptions, and the e-cash scheme can provide unforgeability of e-cash, anonymity of honest customers and efficient traceability of double spending.