Beyond format-compliant encryption for JPEG image

In this work, a format-compliant encryption method with the data embedding feature for JPEG compressed image is proposed. First, DC coefficients are encoded based on the regions induced by the textural information carried by AC coefficients. Second, AC coefficients are scanned in eight different orders and the order that results in the smallest bitstream size is selected. Next, AC coefficients from each block are extracted in the form of Run/Size and Value, and manipulated to significantly increase the scope of permutation. Then the virtual queue decomposition is proposed to embed external information. All the processes are completely reversible where the embedded information can be extracted and the original content can be perfectly reconstructed from its processed counterpart. The performance of the proposed method is verified through experiments using various standard test images and the UCID dataset. The proposed method is also compared against the conventional format-compliant encryption methods, where its superiority in terms of robustness against sketch attacks, suppression of bitstream size increment, and data embedding are highlighted. In the best case scenario, the proposed method is able to generate an encrypted image of the same size as the original image (e.g., 512×512) with more than 5800 bits of additionally embedded information while achieving a compression gain of 1%.