Toward Tight Security of the Galindo–Garcia Identity-based Signature

Abstract

Galindo–Garcia identity-based signature (GG IBS) is an efficient identity-based signature (IBS) whose security is proven under the discrete logarithm (DL) assumption. Since the original security reduction of GG IBS is loose, there are some works to improve the reduction factor. However, such improvements do not achieve the tight security reduction sufficiently, or the efficiency of the resulting scheme is much worse than the original scheme. In this paper, we propose a new improvement of GG IBS. The proposed scheme has a tight security reduction from the decisional Diffie–Hellman (DDH) assumption with respect to a security model which is weaker than that of GG IBS. Our IBS has a better efficiency than the previous improvement of GG IBS whose security is also proven under the DDH assumption.