Study On Reversible Data Hiding

In the recent years, the rapid development of computer networks and the increased use of multimedia data via the Internet have resulted in the faster and more convenient exchange of digital information. On account of the ease of editing and perfect reproduction, it is important to prevent unauthorized manipulation of digital content. Digital watermarking, a technique to embed special labels in digital contents, has led to much research in the domain of information hiding. However, most image watermarking methods introduce distortions to the original content. Often, the embedding distortion is irreversible, i.e. it cannot be removed to recover the original host signal. But some other authentication applications such as medical imagery and military image prohibit the permanent loss of image fidelity during watermarking. It is often desirable to embed a watermark in a reversible way so that the loss of signal fidelity can be remedied by the use of Lossless Authentication techniques.This paper focuses on the theory, methods and realization of lossless data hiding in image. According to different theories, this paper presents two methods for lossless data hiding in spatial domain and frequency domain. The first method present a new lossless data hiding algorithm in spatial domain of digital image.Firstly we modify the histogram of whole image to prevent grayscales from possible overflow/underflow of 0-255, Then make a whole dray level image lots of little blocks. Through bit-shift for every block, we get gaps to embed hiding data. The second method modifies the Histogram of image according to relation of both wavelet coefficient and pixels value to prevent overflow. Then hiding data are embedded in wavelet coefficient. Through reversible wavelet transform, we get the image which bring hiding data. Experimental results show that these two schemes are among the best in the literature in terms of both capacity and visual quality of marked image.