Reversible data hiding scheme in multiple encrypted images based on code division multiplexing

Recently, a reversible data hiding (RDH) scheme based on code division multiplexing (CDM) has been reported, in which secret information and pseudo bits are transformed into spreading sequences. Most sequences may be mutually offset when they are repeatedly embedded, which leads to image quality and embedding capacity improvement. Despite of these advantages, the pseudo bits may cause the image distortion, especially in the low embedding rates. Moreover, it is hard to protect image content when the image is uploaded to cloud server. In order to solve these problems, we propose an RDH scheme based on CDM in multiple encrypted images (RDHMEI) with public key cryptography. The proposed method first encrypted the image using the Paillier homomorphic encryption. Afterwards, the encrypted pixels that have a same coordinate in the multiple images are selected as the elements of the embedding vector. Instead of traditional dual-images based RDH, the proposed method can embed additional bits into the embedding vector while the pixel correlation disappears after encrypting. Experimental results demonstrate the effectiveness and advantages of the proposed method.