Private Blockchain-Assisted Certificateless Public Key Encryption With Multikeyword Search for Fog-Based IIoT Environments

Various sensors are utilized to gather data for the Industrial Internet of Things (IIoT) environments and stored in an adaptable and affordable cloud computing infrastructure. The cloud server performs data analytics intelligently using AI-enabled applications. IIoT data must be encrypted to protect privacy because it is kept on a cloud server, which is untrusted. Nevertheless, there is a difficulty with searching encrypted data, which may be resolved by using a Public key Encryption with Keyword Search (PEKS) method. Furthermore, most existing PEKS schemes are vulnerable to Inside/Outside Keyword Guessing Attacks (IKGAs/OKGAs). Recently, some Certificateless PEKS (CL-PEKS) schemes have been proposed to circumvent certificate management issues, key escrow problems, and IKGA/OKGA. However, they are vulnerable to a malicious Key Generation Center (KGC) attack as they do not satisfy the Girault’s level-3 security. We proposed a private blockchain-assisted CL-PEKS for Multikeyword (BCT-CL-PEMKS) search in a fog-based IIoT environment. The BCT-CL-PEMKS scheme meets the Girault’s level-3 security. It used a private blockchain to manage all the fog nodes. The BCT-CL-PEMKS provides ciphertext indistinguishability, trapdoor indistinguishability, and designated-server testability in the random oracle model. We estimated the computation and communication overheads of BCT-CL-PEMKS and compared them with the other PEKS schemes for 80, 112, 128, 192, and 256-bit security levels.