  With the popularization of digital information technology, the reversible
data hiding in encrypted images (RDHEI) has gradually become the research
hotspot of privacy protection in cloud storage. As a technology that can embed
additional information in the encrypted domain, extract the embedded
information correctly and recover the original image losslessly, RDHEI has
received a lot of attention from researchers. To embed sufficient additional
information in the encrypted image, a high-capacity RDHEI method using adaptive
encoding is proposed in this paper. Firstly, the occurrence frequency of
different prediction errors of the original image is calculated and the
corresponding adaptive Huffman coding is generated. Then, the original image is
encrypted and the encrypted pixels are marked with different Huffman codewords
according to the prediction errors. Finally, additional information is embedded
in the reserved room of marked pixels by bit substitution. Experimental results
prove that the proposed method outperforms the state-of-the-art methods in
embedding rate and can extract the embedded information correctly and recover
the image losslessly.
