Blockchain‐based secure deduplication of encrypted data supporting client‐side semantically secure encryption without trusted third party

Abstract To accommodate the new demand for the deduplication of encrypted data, secure encrypted data deduplication technologies have been widely adopted by cloud service providers. At present, of particular concern is how deduplication can be applied to the ciphertexts encrypted by semantically secure symmetric encryption scheme. Avoiding disadvantages of the existing methods, in this article, we propose a blockchain‐based secure encrypted data deduplication protocol supporting client‐side semantically secure encryption. In the proposed protocol, the smart contracts are deployed by the first file uploader, and then the subsequent uploaders implement an interactive proof of ownership for the same file with the help of the smart contracts executing a cloud data integrity auditing protocol. The smart contracts play the role of the trusted third party and therefore make up for the poor feasibility for the existence of a trusted third party in real scenario. In addition, in the proposed protocol, there is no need for other clients who have uploaded the same file to be online to help the current uploader obtain the encryption key. We also prove its security and evaluate its performance.