Identity-based partially blind signature in the standard model for electronic cash

Partially blind signature allows a signer to explicitly include a piece of common information in a blind signature under some agreement with a receiver. Partially blind signature is a crucial component of electronic cash systems. Recently, some identity-based partially blind signature schemes were proposed. However, all of these schemes are provably secure in the random oracle model. In this paper, we propose an identity-based partially blind signature scheme in the standard model. Our scheme is based on Paterson and Schuldt's identity-based signature scheme. We prove that our scheme has existential unforgeability under the computational Diffie-Hellman assumption and partial blindness. To the best of our knowledge, the proposed scheme is the first identity-based partially blind signature scheme that is secure in the standard model. We give an example of potential application to electronic cash systems using our scheme.