Reversible Data Hiding in Homomorphic Encrypted Images Without Preprocessing

Recently, reversible data hiding in encrypted images (RDH-EI) has been developed to transmit additional data. Besides extracting the hidden data, the original or processed image should be obtained when needed. In this paper, a new RDH-EI method for homomorphic encrypted images is proposed by utilizing the additive homomorphism and self-blinding property in Paillier cryptosystem. Specifically, part of the hidden data may be extracted before image decryption while the rest can be extracted after image decryption. In addition, no preprocessing is required so that homomorphic processing can be performed before data embedding. The experimental results on test images validate that the proposed method is compatible with homomorphic image processing before data embedding. Compared with the state-of-the-art methods, higher embedding capacity can be obtained with the proposed method while the original or processed image can be correctly generated.