Research On Reversible Data Hiding Algorithm In Encrypted Images Base On Prediction Error

The rapid development of the Internet and cloud computing has provided convenience for the transmission of multimedia information.For the purpose of protecting digital images,more and more users encrypt the images and store them in the cloud.Cloud service providers will embed the important data information in the ciphertext images for classification management.Reversible Data Hiding in Encrypted Image(RDH-EI)algorithm can meet the above requirements,which becomes a research hotspot in recent years.This thesis takes the embedding capacity and the decryption image quality as the research object,utilizes the encryption method of XOR and block scrambling,and combines the information hiding algorithm of bit replacement and difference expansion to build the RDH-EI framework and study the separability of the algorithm.Based on this,this thesis proposes two separable RDH-EI algorithms.The main research work is as follows:Combining the XOR encryption and bit replacement algorithm,keeping the low-plane bit information not lost,this thesis proposes the RDH-EI base on reserving room before encryption.The algorithm utilizes the feature of natural image which has high correlation of the high-plane,through the calculation of the prediction error of high-plane,using difference histogram translation method,reversibly embedding part of the least significant bit information in the high-plane,leave room for information hiding.After XOR encryption,the extra information will be embedded in the reserved space by bit replacement algorithm.Information extraction and image restoration on the receiving side are independent of each other.The experimental results show that the selected part of the high order plane is 2<n<8,The lower the selected high-plane is,the larger the embedding capacity is,and the decryption image quality can reach more than 52 dB.This thesis proposes another RDH-EI,which is reversible data hiding in encrypted image base on combining block scrambling and difference expansion algorithm.The algorithm divides the image into 3×3 non-overlapping blocks and then performs global scrambling encryption,which protects the image information content not leaking and maintains the relative position of pixels in each block.The extra information can be extended and embedded by two rounds of difference expansion.The first round of information embedding is embedded by the predicted difference expansion of non-sample pixels,and the second round of information embedding is embedded by sample pixel difference expansion.The receiver can either decrypt the encryption image containing the secret message directly,extract the information using the hidden key,or recover the image after extracting the information first.The experimental results show that the algorithm makes full use of the redundancy between pixels and the scalability of the difference value.And the two-round difference expansion method greatly increases the ratio of the difference that can be used for expansion,thereby increasing the embedding capacity,and the algorithm can be separated.In order to verify the feasibility and effectiveness of the proposed algorithm,the encryption image reversible data hiding framework with XOR encryption and bit substitution are selected,and a GUI simulation system is designed to demonstrate and verify the algorithm intuitively.