A High-capacity Reversible Data Hiding Method in Encrypted Images Based on Block Shifting

Reversible data hiding in encrypted images (RDH-EI) is a new topic drawing more and more attention because of the privacy-preserving requirements from cloud data management. In this paper, a novel reversible data hiding scheme for encrypted image with large embedding capacity is proposed. And it is a client-free RDH-EI scheme in which the RDH algorithm used by the cloud is irrelevant with both the sender and receiver. Different from the previous methods, we propose a block shifting method to transform the original image into the scrambled image which not only looks throughly meaningless, but also obtains a sharp histogram by keeping block correlation meanwhile. For the scrambled image, it is easy for the data hider to reversibly embed data with any plaintext image RDH algorithm such as histogram shifting or lossless compression. The proposed method can achieve real reversibility, that is, data extraction and image recovery are executed with no error. Compared to the previous methods, the experimental results demonstrate that our proposed method increases the embedding capacity in a big range without loss of perfect secrecy.