High-Capacity Reversible Data Hiding for Encrypted Multimedia Data With Somewhat Homomorphic Encryption

This paper proposes a high-capacity reversible data hiding scheme for encrypted multimedia data by using Somewhat Homomorphic Encryption. In an image, three adjacent pixels are selected as a group for the whole process. In the encryption part, the original image is encrypted by an image provider. Then, the encrypted image is sent to data hider. In the data hiding part, two absolute differences can be obtained in each group. The additional data are embedded into the encrypted image by shifting histogram of the absolute differences. Moreover, a sorting technique that sorts the sum of two absolute differences in each group has good effects on reducing image distortion. The encryption and embedding operations are controlled by encryption and embedding/data hiding keys, respectively. If a receiver only has the data hiding key, the additional data can be extracted and the ciphertext can be restored. If the receiver has both the decryption key and the data hiding key, the additional data can be extracted and the original image can be restored. The experimental results have demonstrated the superiority of the proposed method over the existing similar methods.