A Lightweight Privacy-Preserving Ciphertext Retrieval Scheme Based on Edge Computing

With the rapid development of cloud computing and Internet of Things (IoT) technologies, large amounts of data collected from IoT devices are encrypted and outsourced to cloud servers for storage and sharing. However, traditional ciphertext retrieval schemes impose high computation and storage overhead on end users. Meanwhile, IoT devices with limited resources are difficult to adapt to large amounts of data computation and transmission, which leads to transmission delay and poor user experience. In this article, we propose a lightweight privacy-preserving ciphertext retrieval scheme based on edge computing (LPCR) by extending searchable encryption (SE) and ciphertext policy attribute-based encryption (CP-ABE) techniques. First, to avoid network delay and paralysis, we introduce edge servers into LPCR and design a collaboration mechanism between the user side and the edge servers. The user side only needs to accomplish lightweight computation and storage tasks, which greatly reduces their resource consumption. Second, we extend the basic ciphertext policy attribute-based keyword search (CP-ABKS) technique and design the Linear Secret Sharing Scheme (LSSS) access control algorithm with attribute values to hide access policies and attributes. In addition, to improve the retrieval accuracy, the document indexes and query trapdoors are set up by conjunctive keywords to help the cloud server locate exactly the data that the user wishes to query. Formal security analysis verifies that LPCR can achieve the security of chosen plaintext attack (CPA) and chosen keyword attack (CKA), and resist collusion attack. Simulation experiments prove that LPCR is lightweight and feasible.