A New Design of Online/Offline Signatures Based on Lattice

With the rapid development of mobile internet, a large number of lightweight devices are widely used. Therefore, lightweight cryptographic primitives are urgently demanded. Among these primitives, online/offline signatures are one of the most promising one. Motivated by this situation, we propose a lattice-based online/offline signature scheme by using the hash-sign-switch paradigm, which was introduced by Shamir and Tauman in 2001. Our scheme not only has the advantages of online/offline signatures, but also can resist quantum computer attacks. The scheme we propose is built on several techniques, such as cover-free sets and programmable hash functions. Furthermore, we design a specific chameleon hash function, which plays an important role in the hash-sign-switch paradigm. Under the Inhomogeneous Small Integer Solution (ISIS) assumption, we prove that our proposed chameleon hash function is collision-resistant, which makes a direct application of this new design. In particular, our method satisfies existential unforgeability against adaptive chosen message attacks in the standard model.