A Secure and Computable Blockchain-Based Data Sharing Scheme in IoT System

The internet of things (IoT) devices are expected to collect vast amounts of data that support different kinds of applications such as health monitor, smart home, and traffic management. However, its characteristics such as resource-constrained nature, dynamicity, and large-scale growth bring challenges to secure IoT data sharing. Nowadays, blockchain-based ciphertext-policy attribute-based encryption (CP-ABE) was proposed to realize secure IoT data sharing. In blockchain-based CP-ABE data sharing schemes, the data are encrypted and stored in the cloud. Once users want to process the data, they should download and then decrypt the ciphertext in the client-end, and after processing the data, users encrypt and upload the ciphertext onto the cloud. This outweighs the advantage of using cloud computing resources. Fully homomorphic encryption (FHE) and homomorphic signature technology may be adopted to realize ciphertext computation and for correctness checking of ciphertext computation results. In this paper, we propose a secure and computable IoT data sharing system to ensure users enjoying the computation convenience of the cloud-end. Specifically, the proposed system integrates CP-ABE and FHE to realize secure IoT data sharing and ciphertext computation. In addition, we generated homomorphic signatures of ciphertexts to enable users to check the correctness of the ciphertext computation results. Moreover, to supervise the cloud, providing the honest IoT data access control, storage, and computing services for users, we recorded the access policy of the data, the hash of the data, the signature of the ciphertext, and the homomorphic signature of the ciphertext on the blockchain. The performance evaluation and security analysis show the proposed scheme is practical and secure.