Certificateless Public Key Authenticated Searchable Encryption With Enhanced Security Model in IIoT Applications

In Industrial Internet of Things, powerful cloud servers are needed to process substantial sensitive industrial data, which should be encrypted before being uploaded to the cloud. To retrieve encrypted data, certificateless public key authenticated encryption with keyword search (CLPAEKS) is proposed. It has three advantages: 1) no certificate management problem; 2) no key escrow problem; and 3) inside keyword guessing attack resistance. The basic security requirements of current CLPAEKS schemes are ciphertext indistinguishability (CI security) and trapdoor indistinguishability (TI security) in the single-challenge setting. However, these security requirements are incomplete, since some necessary real-world scenarios are not considered: 1) the multichallenge setting to capture scenarios where multiple keywords may be embedded in one file or search query and 2) the fully chosen keyword attack, which allows the adversary to obtain ciphertext or trapdoor of any keyword. In this article, we formalize two enhanced security models for the CLPAEKS system to both capture the multichallenge setting and resist against fully chosen keyword attacks. Then, we provide a cryptanalysis on some of previous CLPAEKS schemes to better understand the necessity of these security models. Furthermore, we propose the first CLPAEKS scheme provably secure in our enhanced security models. Compared with previous CLPAEKS schemes, our scheme provides stronger security guarantee for the privacy of both ciphertext keyword and target keyword. We also evaluate the performance of our CLPAEKS scheme and optimize the efficiency of our scheme by performing most of the computation offline. As a result, the online efficiency of our CLPAEKS scheme is comparable to other schemes optimized using the same techniques.