Research On Reversible Watermarking And The Algorithms In Encryption Domain

Reversible watermarking technique is an important branch in the field of multimedia information security technology. It can’t only preserve the information, but also extracts the watermarking without distortion and exactly recovers the cover image, which makes it possible to apply for the field that the quality of image must be high, such as military image, remote sensing image and medical image. Reversible watermarking in encryption domain is one of reversible watermarking technique, which has the advantages of encryption technology and reversible watermarking technique. It can prevent information leakage and recover the multimedia. This paper introduces some methods about reversible watermarking and the problem in current research in detail. And inspired by prior works, we proposed three new algorithms for reversible watermarking.(1) A novel reversible data hiding method based on adaptive prediction techniques and histogram shifting is proposed. In most natural images, it always contains edge regions and smooth regions. It is not suitable to predict these pixels only using one prediction method. For more precise prediction, an adaptive prediction technique is designed to calculate the prediction errors. As a result, two prediction error histograms are built. Data are embedded in the image by using histogram shifting method. In addition, a new sorting method is applied to histogram shifting. Through the sorting method, the prediction errors with small absolute values are arranged in the front and more embeddable pixels are preferentially processed. Therefore, the number of shifting pixels is decreased if the peaks in the histograms are all dealt with or the capacity is satisfied, which is beneficial to distortion reduction. Experimental results demonstrate that the proposed method acquires greater capacity and higher quality compared with other state-of-the-art schemes.(2) A high capacity reversible watermarking method in encryption domain based on the most significant bits is proposed. In general, the correlation is higher between pixels in nature images. So the most significant bits of adjacent pixels are same or very similar. And the code stream composed with these the most significant bits will very easily compressed. Based on this idea, this paper proposes a high capacity reversible watermarking method in encryption domain based on the most significant bits. The method efficiently improves the capacity. For some images, the capacity can reach lbpp. And through the correlation of image, we can achieve higher quality of directly decrypted image.(3) A low error rate reversible watermarking in encrypted image based on the most significant bits is proposed. Considering the capacity and the correct rate of recovery, the algorithm finds a method to mark the location where the watermarking is embedded. And through the most significant bits of pixels with the marks, the room accommodating the watermarking is vacant. In extraction process, the marks are used to extract the watermarking. And the recover image can be obtained by utilizing the correlation of image. The method can extract the watermarking without distortion. And the error rate of image recovery efficiently reduces.