Identity-Based Online/Offline Encryption Scheme from LWE

Abstract

With quantum computers, the quantum resistance of cryptographic systems has gradually attracted attention. To overcome the shortcoming of existing identity-based encryption (IBE) schemes in resisting quantum attacks, we introduce an IBE scheme based on learning with errors (LWE). In addition, devices with limited computing power are becoming increasingly common in practice, making it increasingly important to improve the efficiency of online computation of encryption algorithms. The classic solution is to directly improve the efficiency of the Gaussian sampling algorithm, thereby increasing the overall efficiency of the scheme. However, our scheme combines the efficient Gaussian sampling algorithm, G-trapdoor, with online/offline method to further improve the online encryption efficiency of the encryption algorithm. Our scheme completes partial computation before knowing the message and receiver’s identity, and once the message and receiver’s identity are obtained, the online part encryption can be efficiently completed. We construct an identity-based online/offline encryption (IBOOE) scheme from LWE with G-trapdoor, improve the efficiency of online encryption while achieving quantum resistant security. We prove the scheme’s security under the standard model for chosen-plaintext attack (CPA). By comparing with relevant schemes in terms of experiments and analysis, our scheme has improved efficiency by 65% to 80% compared to the classical LWE IBE scheme (increasing with LWE security parameters), and by 60% to 70% compared to the recent IBE scheme from LWE. This greatly improves the efficiency of online computing for low-power encryption devices while ensuring security.