Research On Reversible Data Hiding In Image Encryption Domain Based On Block Truncation Coding

With the rise of Internet technology,users store image information in the cloud.The private information in cloud images needs to be protected.The technology of reversible data hiding in encrypted image can provide technical support for cloud storage image security,and has been studied by many scholars.Existing reversible data hiding algorithms in encrypted image are designed around standards such as embedding capacity,image restoration quality,time complexity and security.The reversible data hiding technology in the encryption domain based on block truncation coding has better time performance.This thesis designs two reversible data hiding algorithms in the encryption domain based on block truncation coding.The main work of this thesis has the following three aspects.(1)Research and analysis of absolute moment block truncation coding,interpolation absolute moment block truncation coding and dynamic multi-group absolute moment block truncation coding,analyzed the advantages and disadvantages of the three under different block conditions in compression rate,restoration image quality and time complexity.Interpolation absolute moment block truncation coding and dynamic multi-group absolute moment block truncation coding are improved on the basis of absolute moment block truncation coding.Interpolation absolute moment block truncation coding is mainly used to reduce the compression rate,and dynamic multi-group absolute moment block truncation coding is mainly used to improve image restoration quality.However,the running time of the three coding methods does not exceed 2.5s.By using the characteristics of coding technology to apply it in the data hiding scheme for data embedding,it lays the theoretical foundation for the large-capacity image encryption domain reversible data hiding algorithm based on block truncation coding designed in this thesis.(2)Based on the correlation characteristics of the triples generated by the interpolation absolute moment block truncation coding,a reversible data hiding algorithm in the encryption domain of the block decorrelation interpolation absolute moment block truncation coding is designed.The algorithm divides the image into two parts,performs interpolation absolute moment block truncation coding for the smooth block,and makes full use of the correlation between the high and low average values and the low average values of adjacent blocks to improve the data hiding ability.At the same time,the difference between the smooth block reconstructed by encoding and the original pixel block is preserved as additional information,so that the image can be restored losslessly.Compared with the existing encryption domain reversible data hiding algorithm based on interpolation absolute moment block truncation coding,this algorithm has a higher embedding capacity,the maximum embedding rate of Lena image can reach 2.45 bpp,and the running time is 4.7s.(3)By improving the dynamic multi-group absolute moment block truncation coding,a reversible data hiding algorithm in the encryption domain based on predictive dynamic multi-group absolute moment block truncation coding is designed.The dynamic multi-group absolute moment block truncation coding reference value generated by the image block is correlated,and the compression rate can be effectively reduced by combining it with the prediction method.On the basis of predictive dynamic multi-group absolute moment block truncation coding,the difference between the reconstructed block and the original pixel block is saved so that the image can be restored without loss,thereby designing a reversible data hiding algorithm.The experiment verifies that the maximum embedding rate of Lena image of this algorithm can reach 2.78 bpp,the running time is 3.5s,and it has good performance.