A Flexible Reversible Data Hiding Method in Compressible Encrypted Images

In this paper, we propose a reversible data hiding method in encrypted images, where both the compression efficiency and hiding capacity are flexibly controlled. The proposed method first divides the original image into two regions, e.g., region of interest (ROI) and non-region of interest (non-ROI). In one region, an encryption-then-compression (EtC) system is used for encryption and a histogram shifting based method is adopted for data hiding. Accordingly, lossless compression using image coding standards is effective in this region even after encryption, and also the region can be decrypted without data extraction. In the meanwhile, an MSB prediction based method is introduced in another region. The MSB prediction errors are first detected to recover the original MSBs in the restoration process. Then, exclusive-or operation and MSB replacement are conducted for encryption and data hiding, respectively. This method attains high hiding rate; the rate in this region is around 1 bpp. Experimental results show the effectiveness of the proposed method in terms of hiding capacity and lossless compression efficiency.