Lattice based signature with outsourced revocation for Multimedia Social Networks in cloud computing

摘要

Identity-based signature schemes enable any pair of users to communicate securely and to verify each other's identity without exchanging private or public keys, without keeping key directories, and without using the services of a third party. Such paradigms are very suitable for an emerging scenario of Multimedia Social Networks (MSNs), in which there are a large number of users, dynamic interaction and huge content sharing. A revocable identity-based signature(RIBS) scheme, proposed by Tsai et al., provides a revocation mechanism for controlling user's access dynamically. To capture a realistic and efficient scenario, In 2017, XiaoYing Jia et al. introduced an additional important component, called Cloud Revocation Server(CRS), where most of the computations needed during key-updates are of loaded to the CRS. With the surprising development of quantum computation technology in recent years, IBS schemes mentioned above, based on conventional number theory problem, would become vulnerable. Recently, lattice-based cryptography schemes were proved to be secure against quantum attacks. Although such efficient RIBS scheme based on Computational Diffle-Hellam Problem(CDH) assumption has been proposed, all the lattice-based RIBS do not achieve this realistic and efficient property. In this paper, we propose the first lattice-based RIBS with outsourced Cloud Service Provider(CSP). In our scheme, a user's private key is composed of both an partial private key and a time update key. The time update key is periodically updated by CSP and is transmitted over a public channel. Based on the hardness assumption of Short Integer Solution (SIS), we demonstrate that the proposed lattice-based RIBS scheme with outsourced revocation in cloud computing provides existential unforgeability against adaptive chosen-message attacks in the random oracle. As compared to the existing IBS schemes over lattices, our RIBS scheme has better performance in terms of energy consumption, signature size, signing key size, and the revocation mechanism with public channels. As the underlying lattice problem is intractable even for quantum computers, our scheme would work well in the quantum age.