关键词: 电子现金, 多重息票, 非交互的零知识, 并发安全性, 注册公钥模型

Abstract: The disadvantage of previous multi-coupon schemes is the lack of efficient protocol in which users can decide the maximal number of redemption according to their demands.And another deficiency is that they cannot remain secure in the concurrent case.This article remedied these obstacles by providing two improved systems with concurrent security.The first scheme was obtained by extending the underlying scheme of Blanton with the proof of two committed values and the Sigma-compiler for two round concurrent zero-knowledge argument.The second scheme (i.e.,the strengthened version of the first one) achieved more efficient security reduction by incorporating the straight-line extraction paradigm and removed random oracles by using the non-interactive zero-knowledge argument from homomorphic encryption.Compared with the other strongly unsplittable schemes,the first scheme has better communicational efficiency and the second one does not rely on the random oracle model.

Key words: e-cash, multi-coupon, non-interactive zero-knowledge, concurrent security, the registered public-key model