Identity-based chameleon hash from lattices

Identity-based chameleon hash (IBCH) is a cryptographic primitive with nice properties. IBCH equips each user with a trapdoor and the hash values can be publicly evaluated w.r.t. the identity of any user. On the one hand, it is hard to find collisions for the hash values without the user’s trapdoor. On the other hand, with the help of the user’s trapdoor, finding collisions becomes easy. An important application of IBCH is to upgrade an identity-based signature (IBS) scheme to an on-line/off-line identity-based signature (OO-IBS) scheme. OO-IBS is a useful tool to provide authenticity in lightweight smart devices, since it only involves light on-line computations and does not need key certificate. Up to now, there are many IBCH constructions from traditional number-theoretic assumptions like RSA, CDH, etc. However, none of the existing IBCH schemes achieve the post-quantum security in the standard model. In this paper, we propose a new IBCH scheme from lattices. The security of our IBCH is reduced to a well-accepted lattice-based assumption – the Short Integer Solution (SIS) assumption in the standard model. Our work provides the first post-quantum solution to IBCH in the standard model.