The Reversible Information Hiding Of Gray Image Based On Dividing Image Into Blocks Twice And Histogram Shifting

In nowadays,Internet has become the inseparable part of people's life.How information transform safely has become a hot spot in nowadays' Internet.To cater to the personal and social requests,information hiding as an important branch of information security is developing.Information hiding is a technology that embed the secret information into the carrier,which mostly means media carriers such as digital image,sounds fragments and so on.Reversible information hiding develops from information hiding,it means we can get the secret information and restore the original carrier.My focused research area is the reversible algorithm of space area that based the histogram shifting.To solve the problem that more data embed when divide the picture into blocks,the quality of picture that had secret data become lower,put forward a algorithm for the reversible hiding information algorithm of secondary blocking that based on the gray-level histogram modification algorithm.The algorithm based on image pixel similarity among neighboring areas,dividing the image into several blocks to improve the peak points,but the operation will increase pixels that are modified by shifting operation.It will decrease the quality of images.So to consider the quality of images that embed data and the embedding capacity,we divide smaller blocks second time in every blocks that we first divided,for different type of every smaller blocks,to increase the peak signal to noise ratio,the algorithm handle it in different ways,examples are as follow:For the smaller blocks of first type,which doesn't exist peak point in big blocks,don't operate the block;For the smaller blocks of second type,which exist only one peak point in big blocks,shifting all pixels except peak point;for the smaller blocks of third type,which exist more than two peak points in big blocks,embedding secret data.Meanwhile,based on the algorithm,using the rhombus prediction method to calculate the differences to get the difference histogram,embed secret data by twice.Every embedding takes the different directions to repair the pixels.The last is the result of the experiment data,which show that the improved algorithm according to the experimental data,the algorithm can not only improve the embedding capacity,also can increase the peak signal to noise ratio.