Grouping Strategy Based Secure Cross-User Deduplication in Cloud Storage

Random chunks generation attack is a more sophisticated form of side channel attack in the process of cross-user client side deduplication. By constructing a deduplication request consists of one or more target chunks together with a number of randomly generated non-duplicate ones, the situation that every one of the target chunks is duplicate cannot be differentiated from that none or part of them is duplicate, which hinders the introduction of obfuscation. Once such an attack is launched in a hybrid mode, the risk is even more significant since a proportion of target chunks is replaced with public ones, which makes the existence privacy of remaining target chunks easier to be exposed. In order to deal with these challenges, we propose a novel grouping strategy based secure cross-user deduplication scheme for cloud storage, which takes the lead to achieve security against the hybrid attack mentioned above. Specifically, we propose a secure grouping obfuscation strategy and an aggregated response generation mechanism, allowing the cloud service provider to randomly distribute query tags of chunks in a certain request into several groups, and generate an obfuscated response for each one of them according to an adaptive response table before returning an aggregated result. The security analysis and experimental results show that the proposed scheme is able to achieve resistance against the aforementioned attacks with controllable overhead introduced no matter how many target chunks are involved.