High capacity reversible data hiding with contiguous space in encrypted images

Reversible data hiding in encrypted images (RDHEI) is used to embed secret data into an encrypted image to ensure data security and image privacy. However, a considerable portion of the existing methods do not achieve a high data embedding rate (ER) with complete reconstruction of the original image. Considering the aforementioned limitation, this paper proposes a new RDHEI method with contiguous space. The proposed method pre-processes the original image by dividing it into non-overlapping blocks to determine a label map based on absolute prediction errors. Next, the label map is encoded, and bit-plane shifting is done to create contiguous space for embedding. Thus, the proposed method effectively exploits local and overall image spatial correlation and creates a larger space for embedding in a bit-plane-wise manner. Compared to the state-of-the-art methods, the ER of the proposed method is significantly increased while ensuring complete reversibility and lossless extraction of the hidden data.