Practical identity-based signature without random oracle

To date, most of the constructions of provably secure identity based signature (IBS) scheme are based on the approach of attaching certificates to non-identity based signatures in the random oracle. In ACISP´06, Paterson et al. proposed the first direct construction of IBS in the standard model. However, Paterson et al.´s scheme has a large size of the public parameter, which is not suitable for environments with limited storage capacity. In this paper, we proposed an efficient provably secure IBS scheme in the standard model based on bilinear pairings. To the best of our knowledge, our scheme is another direct construction and more efficient by reducing about half the size of public parameters than Paterson et al.´s scheme. Assuming the intractability of the Computational Diffie-Hellman problem, our IBS scheme is unforgeable under an adaptive chosen-message attack without resorting to random oracle.