Paper 2014/859

Provably secure pairing-free identity-based partially blind signature scheme and its application in online e-cash system

SK Hafizul Islam and G. P. Biswas

Abstract

The blind signature scheme permits the user to acquire a signature from the signer; however, the message and the final signature are unknown to the signer. In a partially blind signature (PBS) scheme, the signer can explicitly incorporate a common information in the signature based on some agreement with the user and without violating the blindness property. Many PBS schemes have been proposed recently either by using certificate authority-based public infrastructure (CA-PKI) or pairing along with map-to-point function. The CA-PKI-based PBS scheme needs huge computation and storage to keep public keys and certificates. On the other hand, pairing and map-to-point function are costly operations. Thus, the ID-PBS scheme without pairing is more appropriate for real environments, and an efficient pairing-free ID-PBS scheme is proposed in this paper. In the random oracle model, our scheme is analyzed to be provably secure. The proposed scheme is used to design an online e-cash system, in which a bank agrees on a common piece of information with a customer and can blindly sign some messages. It may be noted that our e-cash system has the properties of unforgeability, unlinkability, and non-deniability and can prevent the double-spending of e-cash.