RO-cash: An efficient and practical recoverable pre-paid offline e-cash scheme using bilinear pairings

Nowadays, various electronic commerce services can be found and are widely used in the Internet due to the mature of information and network technologies. A practical and flexible electronic payment system is one of the key success factors in electronic commerce. Most of the pre-paid anonymous e-cash schemes do not provide lost money recovery. Also, the communication and computation cost of most existing anonymous payment schemes is still high. In this paper, we propose RO-cash, a practical and flexible recoverable pre-paid offline e-cash scheme using bilinear pairing. In RO-cash, we use bilinear pairings in elliptic curves to reduce the computation and communication cost. By distributing the power of a single bank authority to the bank manager and the auditor, the untraceability can be preserved even if the bank manager is not honest in lost-coin recovery. Since our proposed scheme is an offline scheme, it is suitable for the real world environment in which the network connection between a shop and the bank server may not be available during the payment phase. Also, since our proposed scheme is a general scheme, other e-cash schemes with nice properties, e.g. D-cash, PayWord, AOMPS, ownership-claimable e-cash, scheduled e-cash, etc., can be directly applied to our scheme without changing the underlying system structure. This will make our scheme more flexible for attracting customers to use different value-added services.