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Separable High Capacity Reversible Data Hiding Algorithm for Encrypted Images

This paper presents a separable Reversible Data Hiding Algorithm for Encrypted Images (RDHEI) that consists of three phases. The encryption phase in the algorithm circularly shifts the columns in the image by a random amount, blocks the image into equal and regular blocks and maps them to irregular blocks generated based on Hilbert filling curve, and finally complements a random subset of the blocks. The embedding phase is essentially an adapted version of the modification of the prediction errors algorithm that is applied to each block in the encrypted image independently. In the decryption phase, and since the algorithm is separable, the user can extract the data only, decrypt the image only, or can perform both actions depending on the type of keys he has. When compared to a very similar and recent algorithm, performance evaluation proved the ability of the proposed algorithm in increasing the embedding capacity with reasonable quality of the directly decrypted image. In terms of the security, the analytical and quantitative assessment showed the superiority of the proposed algorithm in protecting the encrypted image.