A high-capacity reversible data hiding method for homomorphic encrypted images

Recently, reversible data hiding in encrypted images has been developed to transmit useful data while the original images can be perfectly recovered when needed. In this paper, a new method is proposed for homomorphic encrypted images so that part of the hidden data can be extracted in encrypted domain and the rest are extractable after image decryption. Specifically, a plain-text image is preprocessed by reversibly embedding the bit values of some pixels into the image. The preprocessed image is encrypted in Paillier cryptosystem and two embedding algorithms are applied on the encrypted image in succession. Compared with the state-of-the-art schemes, higher embedding capacity can be achieved by applying the proposed method, respectively for data extraction before and after image decryption. Compared with the schemes with similar properties, better performances are achieved with the proposed method in terms of quality of directly decrypted image with respect to data hiding rate.