Cloud computing promises great advantages in handling the exponential data growth. Secure deduplication can greatly improve cloud storage efficiency while protecting data confidentiality. In the meantime, when data are outsourced to the remote cloud, there is an imperative need to audit the integrity. Most existing works only consider the support for either secure deduplication or integrity auditing. Recently, there have been some research efforts aiming to integrate secure deduplication with integrity auditing. However, prior works are unsatisfactory in that they suffer from the leakage of ownership privacy and forgeability of auditing results for low-entropy data. In this paper, we propose a new scheme that delicately bridges secure deduplication and integrity auditing in encrypted cloud storage. In contrast with prior works, our scheme protects the ownership privacy and prevents the cloud service provider from forging the auditing results for low-entropy data. Furthermore, we propose a blockchain-based mechanism that helps to ensure key recoverability and reduce local storage cost of keys. Formal analysis is provided to justify the security guarantees. Experiment results demonstrate the modest performance overhead of our scheme.

In cloud storage systems, secure deduplication plays a critical role in saving storage costs for the cloud server and ensuring data confidentiality for cloud users. Traditional secure deduplication schemes require users to encrypt their outsourced files using specific encryption algorithms that cannot provide semantic security. However, users are unable to directly benefit from the storage savings, as the relation between the actual storage cost and the offered prices remains not transparent. As a result, users may be unwilling to cooperate with the cloud by encrypting their data using semantically secure algorithms. Moreover, data integrity is a significant concern for cloud storage users. To address these issues, this paper proposes a novel transparent and secure deduplication scheme that supports integrity auditing. Compared to previous works, our design can verify the number of file owners and the integrity through one-time proof verification. It also protects the private contents of files and the privacy of file ownership from malicious users. Moreover, our scheme includes a batch auditing method to simultaneously verify the numbers of file owners and the integrity of multiple files. Theoretical analysis confirms the correctness and security of our scheme. Comparison results demonstrate its competing performance over previous solutions

To implement encrypted data deduplication in a cloud storage system, users must encrypt files using special encryption algorithms (e.g., convergent encryption (CE)), which cannot provide strong protection. The confidential level of an outsourced file is determined by the user himself/herself subjectively or by the owner number of the file objectively. These files owned by a few users are considered strictly confidential and require strong protection. In this paper, we design, analyze and implement LSDedup, which attains a high storage efficiency while providing strictly confidential files (SCFiles) with strong protection. LSDedup allows cloud users to securely interact with cloud servers to check the confidential level of an outsourced file. Users encrypt the SCFiles using standard symmetric encryption algorithms to achieve a high security level, whereas encrypting the less confidential files (LSFiles) using CE such that cloud servers can perform deduplication. LSDedup is designed to prevent cloud servers reporting fake confidential level and a fake file user claiming the ownership of the file. Formal analysis is provided to justify its security. Besides, we implement an LSDedup prototype using Alibaba Cloud as backend storage. Our evaluations demonstrate that LSDedup can work with existing cloud service providers’ APIs and achieves modest performance overhead.

Secure deduplication over encrypted data can greatly improve cloud storage efficiency and protect data privacy. Recently, there have been some research efforts aiming at designing secure deduplication schemes with the assistance of key servers (KSs). However, prior works are unsatisfactory in that they suffer from some limitations such as security degradation (the leakage at partial KSs will lead to all the ciphertexts being subject to offline brute-force attacks) or lack of scalability for handling the change of KSs. In this paper, we propose a new secure deduplication scheme for large-scale cloud storage service, which, to our best knowledge, is the first server-aided scheme that supports both tolerance of partial KSs leakage and dynamic change of KSs. Our scheme divides all the KSs into multiple groups and each KS group keeps a randomly generated secret key using threshold cryptography. We design a file-related KS group selection mechanism for assisting encryption key generation, which guarantees that the identical files of different users can be encrypted using the same keys. Our scheme is designed to update the KS groups regularly for supporting the joining and leaving of the KSs as well as maintaining long-term security. We leverage the blockchain to help divide KSs into groups in a fair way and securely migrate group secret keys during KS group updating. Formal analysis is provided to verify the correctness of our scheme and justify its security, and both theoretical and experimental results demonstrate that it has modest performance overhead.

With the growing popularity of cloud computing, sharing media data through the cloud has become a common practice. Due to high information redundancy, media data take up a significant amount of storage space. Moreover, similar media data may have the same visual effect, resulting in unnecessary duplication. Thus, it can greatly improve the cloud storage efficiency by performing deduplication to the similar media data stored on the cloud. However, data privacy is a growing concern in cloud-based service. In this paper, we present SimLESS, a secure deduplication system for similar data in cloud media sharing. SimLESS allows the cloud to perform deduplication over the encrypted similar media data of different distributors while protecting the confidentiality and ownership of the data. When uploading a media file, SimLESS allows the distributor to set a distance threshold, and the cloud performs deduplication only when there is a file on the cloud whose distance from the file being uploaded is smaller than the threshold. Additionally, we provide fine-grained access control for distributors to ensure that only authorized media consumers can access the data. Furthermore, our system prevents any distributor from claiming ownership of a media file using only the tag of a similar file. We formally analyze the security of SimLESS and implement a system prototype to evaluate its performance. Our experimental results demonstrate that the computation and communication costs of SimLESS are practically affordable.