Effective reversible data hiding in encrypted image with privacy protection for image content

• A novel reversible data hiding scheme in encrypted image is proposed.
• Data hiding is conducted with elaborate selection for partial pixels to be flipped.
• Secret bits can be extracted by adaptive smoothness evaluation in isophote direction.
• Our scheme has better decrypted image quality and higher image recovery accuracy.

In this paper, we propose a novel reversible data hiding scheme in encrypted image. The content owner encrypts the original image with the encryption key to achieve privacy protection for image content, and then, each block of the encrypted image is embedded with one secret bit by the data hider using the data-hiding key. Through the elaborate selection for partial pixels to be flipped, data hiding process only conducts slighter modifications to each block, which leads to significant improvement of visual quality for the decrypted image. The receiver can easily decrypt the marked, encrypted image using the encryption key, and then, through the data-hiding key and an adaptive evaluation function of smoothness characteristic along the isophote direction, secret data can be extracted from the decrypted image, and the original image can further be recovered successfully. Experimental results demonstrate the effectiveness of the proposed scheme.