Transferable conditional e‐cash with optimal anonymity in the standard model
Jiangxiao Zhang, Hua Guo, Zhoujun Li, Chang Liang Xu · IET Information Security · 2014
Transferable conditional electronic‐cash (e‐cash) allows the recipient of a coin in a transaction to transfer it in a later payment transaction to the third person based on the outcome not known in advance. Anonymity is a very important property for a transferable conditional e‐cash. However, none of the existed transferable conditional e‐cash achieve the optimal anonymity because of its special structure, that is, introducing transferability in the conditional e‐cash. In this study, they novelly present a transferable conditional e‐cash scheme using a totally different structure, that is, adding condition into the transferable e‐cash. Thanks to employing Groth–Sahai proofs systems and commuting signatures, the new transferable conditional e‐cash satisfies optimal anonymity. Accordingly, they present an extended security model by introducing a publisher who is responsible for publishing two outcomes of a condition. Then, they prove the new scheme's security in the standard model. Compared with the existing transferable conditional e‐cash, the efficiency of the new scheme is also improved since the size of the computation and communication is constant.