Scalable and Popularity-Based Secure Deduplication Schemes With Fully Random Tags.

It is non-trivial to provide semantic security for user data while achieving deduplication in cloud storage. Some studies deploy a trusted party to store deterministic tags for recording data popularity, then provide different levels of security for data according to popularity. However, deterministic tags are vulnerable to offline brute-force attacks. In this paper, we first propose a popularity-based secure deduplication scheme with fully random tags, which avoids the storage of deterministic tags. Our scheme uses homomorphic encryption (HE) to generate comparable random tags to record data popularity and then uses the binary search in the AVL tree to accelerate the tag comparisons. Besides, we find the popularity tamper attacks in existing schemes and design a proof of ownership (PoW) protocol against it. To achieve scalability and updatability, we introduce the multi-key homomorphic proxy re-encryption (MKH-PRE) to design a multi-tenant scheme. Users in different tenants generate tags using different key pairs, and the cross-tenant tags can be compared for equality. Meanwhile, our multi-tenant scheme supports efficient key updates. We give comprehensive security analysis and conduct performance evaluations based on both synthetic and real-world datasets. The results show that our schemes achieve efficient data encryption and key update, and have high storage efficiency.