Fair Multiple-bank E-cash in the Standard Model

Multiple-bank e-cash (electronic cash) model allows users and merchants to open their accounts at different banks which are monitored by the Center Bank. Some multiple-bank e-cash systems were proposed in recent years. However, prior implementations of multiple-bank e-cash all require the random oracle model idealization in their security analysis. We know some schemes are secure in the random oracle model, but are trivially insecure under any instantiation of the oracle. In this paper, based on the automorphic blind signature, the Groth-Sahai proof system and a new group blind signature, we construct a fair multiple-bank e-cash scheme. The new scheme is proved secure in the standard model and provides the following functionalities, such as owner tracing, coin tracing, identification of the double spender and signer tracing. In order to sign two messages at once, we extend Ghadafi’s group blind signature to a new group blind signature. The new signature scheme may be of independent interest.