An Improved Reversible Data Hiding in Encrypted Image Method Based on Block Selection

For reversible data hiding in encrypted image (RDHEI), the most important problem is the conflict between reversibility and embedding capacity. Reversibility has been realized by existing methods, however, the embedding capacity is still too low for practical RDHEI applications. To settle this problem, an improved RDHEI method is proposed in this article by presenting a block selection mechanism. Since extraction error occurs on blocks from which the fluctuation function fails to identifies the flipped part, we propose to distinguish these exceptional blocks from extraction-correct-block (ECB) (i.e., pixel block from which the hidden data can be exactly extracted) and embed additional data into only ECBs. In this way the minimum block size can be adopted to pursue high capacity. To guarantee reversibility, a new self-embedding method is proposed to embed the auxiliary information into the cover image. Finally, a new fluctuation function is also proposed to provide more ECBs and thus further improve the embedding capacity. Experimental results show that the proposed method not only achieves significant improvement in capacity but also guarantees lossless data extraction and perfect image recovery.