RDH technique for image encryption

In this paper, a novel approach of reversible data hiding (RDH) technique is used to embed additional information in the encrypted images is introduced. Since it maintains the excellent property that the original image can be losslessly recovered after embedded data is extracted while protecting the image content's confidentiality. The previous methods embed data by reversibly vacating room from the encrypted images, which may be subject to some errors on data extraction and/or image restoration. To propose a novel method by reserving room before encryption with a traditional RDH algorithm, and thus it is easy for the data hider to reversibly embed data in the encrypted image. This method can achieve real reversibility, that is, data extraction and image recovery are free of any error. This novel method can embed more than 10 times as large payloads for the same image quality as the previous methods, such as for PSNR=40dB.