Secure ID-Based Blind Signature Scheme without Random Oracle

The known construction of an identity-based blind signature scheme that is secure in the standard model is based on a generic approach which attaches a certificate to an ordinary (i.e. non-identity-based) blind signature scheme, and thus the identity-based blind signature scheme constructed by this method is inefficient and has long signature size. In this paper, based on the identity-based encryption scheme proposed by Gentry recently, we present a direct construction of an identity-based blind signature scheme. Our identity-based blind signature scheme is computationally efficient and the signature is short. We prove that our scheme is concurrently secure with a tight security reduction in the standard model assuming that the q-SDH problem is hard.