A High Capacity Multi-Level Approach for Reversible Data Hiding in Encrypted Images

This paper proposes a novel method of reversible data hiding in encrypted images (RDH-EI). We first provide an RDH-EI approach using single-level embedding, in which three parties are involved, including an image owner, a data hider, and a recipient. The image owner encrypts an original image into a ciphertext image. After dividing the original image into blocks, the owner pseudo-randomly permutes all blocks by a permutation key. With an encryption key, the image owner further encrypts the contents of all blocks using a stream cipher algorithm, during which pixels inside each block share the same stream bytes. Once the encrypted image is uploaded onto the server, a data hider embeds additional messages into the ciphertext. The data hider divides the encrypted image into blocks and selects peak pixels from each block using an embedding key. With the peak pixels, the data hider embeds an additional message using histogram shifting inside each block. On the receiver side, a recipient extracts the hidden message using the embedding key, and losslessly recover the original image with the permutation key and the encryption key. Based on the single-level algorithm, we further construct a multi-level approach. The embedding process is iteratively used to generate the marked encrypted images. Compared with state-of-the-art works, the proposed method achieves a better embedding efficiency and an error-free recovery.