Research On Reversible Data Hidingalgorithm In Encrypted Images Byreserving Room Before Encryption

With the advent of the information age,people's information exchange becomes more and more frequent.On many social platforms,people are more and more willing to share their work and life with images,Therefore,how to effectively protect the image security has become an important issue.To solve this problem,researchers combine encryption technology with information hiding technology,In this way,not only the image content can be protected by encryption technology,but also the encrypted image can be embedded by information hiding technology,so as to realize copyright protection and integrity authentication,at the receiving end,the legitimate receiver can get the lossless restored image and the accurate embedded information.,this technology is called the reversible data hiding in encrypted images.In the research of reversible data hiding in encrypted images,this paper first introduces the research background and status quo of this technology,and according to the needs of many application scenarios,the reserving room before encryption algorithm with high embedding capacity is selected as the key research object.In order to facilitate the expansion of the following text,the commonly used encryption algorithm,information hiding algorithm and evaluation index of the algorithm are also introduced.This thesis analyzes that a reversible data hiding in encrypted images algorithm based on compressed classification does not make full use of the pixel correlation of the original image,using the idea of pre-encrypted reserved space algorithm,the original image pixels are pre-processed differently,the difference between adjacent pixels makes the original image change and sink after pretreatment.,and in the stage of classification and compression,more redundant space can be obtained,which improves the embedding capacity.The experimental results show that the improved algorithm not only greatly improves the embedding capacity,but also restores the image as lossless as the original algorithm.This thesis analyzes that a reversible data hiding in encrypted images algorithm with reserving room before encryption has two problems — — On the one hand,in the pre-processing stage before encryption,the central pixel does not participate in the classification of the pixels,which leads to the inaccurate classification of the pixels,and also makes the central pixel inaccurate in the information extraction and image restoration stage;On the other hand,in the stage of information extraction and image restoration,the mean value prediction method adopted by the algorithm for the central pixel is too rough,whichmakes the recovery result of the central pixel different from the original value.In order to solve these two problems,in the pre-processing stage of encryption,the central pixel can be classified more accurately by modifying the complexity calculation formula,and then in the information extraction and image restoration stage,the central pixel can be predicted more accurately by referring to a weighted prediction algorithm.The experimental results show that the improved algorithm can greatly improve the embedding capacity at the expense of minimal restoration image quality.Finally,the GUI of the improved algorithm in Chapter 3 is designed to verify the feasibility of the improved algorithm and to facilitate researchers to verify the improved algorithm.