An Off-line E-Cash Scheme based on Group Blind Signature Scheme

In this paper we have described the signature scheme inwhich an individual can sign a document ormessage onbehalf of entire group. Here, a group blind signaturescheme has been proposed. Our scheme combines the already existing notions of blind signatures and group signatures. It is an extension of Camenisch and Stadler'sGroup Signature Scheme [12] that adds the blindness property.One important requirement of electronic cash systems is the anonymity of customers.Unconditional anonymity is also very well suited to support criminals inblackmailing. Chen, Zhang and Wang suggested an offline electroniccash scheme[10] to prevent blackmailing by using the group blind signature. In their payment system, they used a group signature scheme of Camenisch and Stadler for large groups which is not secure.In this paper we improve these electronic cash systems to prevent blackmailing, money launderingand illegal purchases by using a secure coalitionresistant group blind signature scheme.