【作者】 郭俊；

【导师】 陈帆；

【作者基本信息】 西南交通大学 ， 信息与通信工程， 2019， 硕士

【摘要】 互联网和云计算的快速发展,为多媒体信息的传播提供了方便,出于保护数字图像的目的,越来越多的用户将图像加密后存储在云端,云服务者会将标签信息嵌入在密文图像,对其进行分类管理。加密图像可逆信息隐藏(Reversible Data Hiding in Encrypted Image,RDH-EI)算法能兼顾上述需求,成为近年来的研究热点。本文以嵌入容量与解密图像质量为研究对象,采用异或与块置乱的加密方法,结合位替换与差值扩展的信息隐藏算法,搭建RDH-EI框架,研究算法的可分离性,基于此,本文提出了两种可分离的RDH-EI算法,主要研究工作如下:结合异或加密与位替换,保留低位比特信息不丢失,提出了加密前预留空间的RDH-EI算法,该算法利用自然图像高位平面相关性高的特点,通过计算高位平面的预测误差,采用差值直方图平移方法,将部分最低位比特信息可逆地嵌入在高位平面中,为信息隐藏预留空间。异或加密后,根据预留的空间使用位替换方法嵌入额外信息,接收端信息提取与图像恢复相互独立,实现了算法的可分离。实验结果表明,可选择的部分高位平面为2<n<8,且选择的高位平面越少,嵌入容量越大,解密图像质量能达52dB以上。提出一种结合块置乱和预测误差扩展的加密图像可逆信息隐藏算法,该算法将图像分为3×3互不重叠的块并进行全局置乱加密,保护图像信息内容不泄露同时维持每个块内像素相对位置不变;额外信息通过两轮差值扩展嵌入,第一轮信息嵌入由非采用像素的预测差值进行扩展,第二轮信息嵌入通过采用像素差值扩展;接收端既可以对含秘密文图像直接解密,也能使用隐藏密钥提取信息,也可以先提取信息再恢复图像。实验结果表明,算法充分利用像素间的冗余度与差值的可扩展性,采用两轮差值扩展方法,大大提高了可用于扩展的差值比例,进而提升了嵌入容量,且算法实现了可分离。为验证所提算法的可行性与有效性,选择了异或加密与位替换的加密图像可逆信息隐藏框架,设计GUI仿真系统,直观演示并验证算法。更多还原

【Abstract】 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.更多还原