High-capacity reversible data hiding in encrypted images by prediction error

• Two reversible data hiding methods in encrypted images are proposed.
• Improved reversibility is obtained by the two methods.
• Visual quality of lossy recovered image by the two methods is high.
• The number of incorrect bits is significantly reduced by the joint method.

In recent years, signal processing in encrypted images received much attention from academia due to the privacy preserving property. Reversible data hiding in encrypted images is a technique that embedded additional data into an encrypted image without accessing the content of the original image, the embedded data can be extracted and the encrypted image can be recovered to the original one. In this paper, two reversible data hiding methods in encrypted images, namely a joint method and a separable method, are introduced by adopting prediction error. In the joint method, data extraction and image reconstruction are performed at the same time. The reversibility, number of incorrect extracted bits are significantly improved while maintaining good visual quality of recovered image, especially when embedding rate is high. In the separable method, data extraction and image recovery are separated. The separable method also provides improved reversibility and good visual quality of recovered image for high payload embedding.