Private Blockchain-Assisted Certificateless Public Key Encryption With Multi-Keyword 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 AIenabled 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 (IKGA/OKGA). 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 Giraults Level-3 security. We proposed a private blockchain-assisted certificateless PEKS for multi-keyword (BCT-CL-PEMKS) search in a fogbased IIoT environment. The BCT-CL-PEMKS scheme meets Giraults Level-3 security. It used a private blockchain to manage all the fog nodes. The BCT-CL-PEMKS provides ciphertext indistinguishability, trapdoor indistinguishability, and designatedserver testability in the random oracle model. We estimated the computation and communication overheads of BCT-CL-PEMKS and compared them with other PEKS schemes for 80, 112, 128, 192, and 256-bit security levels.