Ownership-attached unblinding of blind signatures for untraceable electronic cash,

In an untraceable electronic cash protocol based on blind signatures, an identified customer can withdraw a blinded electronic cash from the bank and the unblinding operation is adopted by the customer to transform the blinded electronic cash into a valid one. Before performing the operation, the blinded electronic cash is protected well since attackers cannot convert it into a valid electronic cash without the blinding factor corresponding to the operation. However, after unblinding, the electronic cash will suffer from the theft attacks since it is not protected by any security mechanism. This paper introduces a new unblinding operation called ownership-attached unblinding which attaches the identities of a designated payee and a specified transaction to the blinded electronic cash and then produces an ownership-attached electronic cash other than a bare one such that the cash can withstand the theft attacks during the entire transaction because it is valid for the designated payee and the specified transaction only. Further0020-0255/$ see front matter 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.ins.2004.10.010 * A partial result of this research was presented at the 14th International Conference on Information Networking, Hsinchu, Taiwan, January 26–28, 2000. This research was partially supported by the National Science Council of the ROC (Taiwan) under grant NSC 92-2213-E-110-035. * Tel.: +886 7 5252000x4346; fax: +886 7 5254301. E-mail address: [email protected] (Chun-I Fan). 2 Chun-I Fan / Information Sciences xxx (2004) xxx–xxx ARTICLE IN PRESS more, the proposed scheme does not largely increase the computation cost required for each customer so that it also is a customer efficient protection solution for untraceable electronic cash and especially suitable for mobile clients and smart-card users. 2004 Elsevier Inc. All rights reserved.