New blind signcryption schemes with application to E-cash systems

Signcryption is a well-known cryptographic primitive that achieves various security goals including confidentiality of communications, source authentication, and integrity of message contents and ensuring non-repudiation. In e-cash systems, customers prefer to spend their e-coins anonymously. Blind signatures have been developed to meet this requirement. In the present paper, two new blind signcryption schemes are proposed in order to combine the functionalities of both primitives in a single logical step. The first one is tailored for traditional public key infrastructures; while the second one is an identity-based scheme. The proposed schemes have been designed with an eye on applications to e-cash systems and thus overcoming shortcomings in earlier attempts in blind signcryption. The two schemes are computationally efficient promoting their use in practical scenarios. The schemes involve three parties. In e-cash scenarios, these are the bank, the e-coin acquirer (customer) and the merchant which deposits the e-coin in his bank account.