Scrambling–embedding for JPEG compressed image

• Degrade image quality while embedding external data in a JPEG compressed image under a single framework.
• Achieve scrambling–embedding using the properties derived from the components (i.e., DC coefficient and AC coefficient) of a JPEG compressed image.
• Minimize the bitstream size increment caused by scrambling–embedding, which is inevitable for the conventional methods.
• Achieve scalability in both image quality degradation and data payload.
• Achieve complete reversibility.

This paper proposes a novel reversible unified information hiding method for the JPEG compressed image, aiming to achieve scrambling and external data insertion simultaneously. The properties of DC coefficients, energy of AC coefficient block, and run of zero AC coefficients are exploited. Two techniques are proposed to degrade the perceptual quality while manipulating the DCT coefficients for data embedding. Most of the existing unified information hiding methods are designed to operate in the spatial domain and their direct application to the compressed domain such as JPEG will lead to large bitstream size increment. Thus, the proposed techniques aim to minimize the bitstream size increment while offering comparable performance with respect to the current state-of-the-art methods. Experiments are conducted to measure the performance of the proposed unified method by using the UCID (Uncompressed Color Image Database) database and standard test images. Results suggest that the effective data payload ranging from 32 to 10238 bits and SSIM value ranging from 0.0548 to 0.9432 are achieved for the UCID database. The proposed method are also compared with the conventional methods in terms of effective data payload, image quality degradation, bitstream size increment and robustness against multiple sketch attacks.