A Fair Off-line Electronic Cash System Based On Traceable Dynamic Group Signature

Electronic cash is cash in an electronic form. Compared with the troditional cash, electronic cash possess a digitized representation and storage form, and have the properties of anonymity, unforgeability and unframability, which can satisfy people's demand to trade conveniently and quickly through the network.Electronic cash has become a research focus of scholars around the world. Although the electronic cash has many advantages and characteristics, but there are still some key technical problems to be studied. Known constructions in the literature suffer from at least one of the following limitations:(1) weak security, the security of systems are always relying on the random oracle model; (2) the incomplete function design, such as nonsupport multiple bank setting and users dynamically joining; (3) the interaction in the system is so much that the communication cost is prohibitively expensive, which would directly lead to the difficulty of electronic cash system universally applicable.Therefore, in this paper based on the theoretical research and analysis of the exsiting electronic cash systems, we make an intensive study focused on the above problems. To acheive members dynamicly joining and the group signature traceability, we proposed a new traceable dynamic group signature scheme. The scheme is based on the BSZ security model and Waters signature, which realize the group signature anonymity and unforgeability. Then, based on the proposed scheme, we construct a fair off-line electronic cash system in standrard model, which is anonymous against adaptive chosen ciphertext attack (CCA). Then, we give the strictly security proof for the proposed system in the standard model that it is with CCA anonymity, unforgeability traceability and no double-spending. Finally, we design and i mplement the prototype electronic cash system and test its core functionality.Finally, we design and implement the prototype electronic cash system. The electronic cash system in this paper mainly includes four entities:the central bank, the local Bank, the customer and the merchant. Compared with traditional electronic cash system, the proposed system achieves multiple banks construction, which makes the central bank free from issuance for electronic cash every time, thus effectively solving the performance bottleneck problems in electronic cash system. To achieve non-interactive anonymous authentication in every protocol, the system takes use the Groth-Sahai non-interactive zero-knowledge proof technology which can improve the security and the communication efficiency in cash transaction. Performance analysis shows that, compared with the existing similar systems, the proposed system is more efficient in communication without impacting the computation cost.