Reversible data hiding in encrypted images using multiple Huffman coding based on optimal block allocation

As a booming technique in the field of information security, reversible data hiding in encrypted images has attracted great concern because secret data can be recorded in the encryption domain without knowing the related encryption key and the content of original images. In this paper, a fully reversible data hiding method with high embedding capacity is proposed based on optimal block allocation with full consideration of distinct pixel characteristics. The occurrence frequency of most significant bits in smooth blocks is used to obtain embeddable space. For fluctuant blocks, a cascaded two Huffman coding is innovatively designed to compress most significant bits of each pixel to generate more spare rooms. To enhance the security, not only the original image is encrypted based on sequences generated with the high-dimension chaotic system, but also the encrypted image containing secret data is further scrambled. Compared with some state-of-the-art methods, the experimental results and analysis demonstrate that the proposed method has larger embedding capacity using different test images and image databases.