Research On The Security Of Reversible Data Hiding Algorithm In Encrypted Image Based On A Combinatorial Scrambling

With the development of the Internet,the network has penetrated into people’s daily life,and more and more users store their digital images in the cloud.With the occurrence of many user privacy leakage incidents caused by cloud storage,how to ensure the security of users’ digital image privacy in the cloud storage environment has become the focus of attention.To this end,the researchers proposed the Reversible Data Hiding in Encrypted Image(RDH-EI).As an important technology to ensure the security of personal privacy information,the security performance of the RDH-EI algorithm cannot be ignored.This thesis will start with the security research of RDH-EI algorithm and study the existing RDH-EI.Since the RDH algorithm in RDH-EI is reversible,this makes the ciphertext image containing secrets can be directly converted into a ciphertext image when the RDH algorithm is disclosed.Therefore,the focus of the research on the security of RDH-EI algorithm is to study the security performance of image encryption algorithm.Since the combinatorial scrambling image encryption is widely used because of its high algorithm embedding capacity and double encryption to ensure the security of image content.Based on the existing combinatorial scrambling encryption algorithms,this thesis proposes two known plaintext attack algorithms based on the non-zero-digit number feature,and points out the potential security risks existing in the combinatorial scrambling encryption algorithms.The main work are as follows.Aiming at the redundant space transfer encryption algorithm in the combinatorial scrambling encryption algorithm,the reasons why it can resist the existing known plaintext and ciphertext only attacks are firstly analyzed.The reason is that the algorithm divides the image into blocks for bit plane scrambling,which effectively changes the statistical characteristic of the bit plane and improves the algorithm’s anti-attack ability.Then the characteristic of the encryption algorithm is analyzed,the non-zero-digit number of the image block are defined,the feature of the non-zero-digit number in the image block are obtained,and the invariance of the feature of the non-zero-digit number before and after image encryption is pointed out.The image blocks are then divided equally based on this feature to estimate the block scrambling key and the bit plane scrambling key.Since the attack results under a pair of known plaintext attack needs to be improved,a multi-pair known plaintext attack method is proposed.The experimental results show that under the 4×4 block,the correct rate of the block scrambling key estimated by a pair of known plaintext attack is as high as89%,and the decrypted image has leaked the original image content.Considering the particularity of bit plane scrambling in the redundant space transfer encryption algorithm,the feature of group rearranged non-zero-digit number is obtained on the basis of the feature of the non-zero-digit number,and the consistency of this feature before and after encryption is pointed out,which makes the block scrambling key estimate is possible.In the equivalent set based on the feature of group rearranged non-zero-digit number,due to the high error rate of random matching image blocks,this thesis proposes a finite backgeneration algorithm.The algorithm decrypts the ciphertext image by exhaustively enumerating all the bit plane scrambling keys,and judges whether the pixel values of the plaintext image block and the decrypted image block are consistent to correctly match the image block,which improves the estimation accuracy of the block scrambling key.At the same time,the possibility of the bit plane scrambling key is reduced by comparing the pixel values,and the estimation accuracy of the bit plane scrambling key is further improved.The experimental results show that the known plaintext attack method based on the feature of group rearranged non-zero-digit number and finite back-generation algorithm,under 3×3blocks,the correct rate of block scrambling key estimated by a pair of known plaintext attack is as high as 100%.Compared with the known plaintext attack results based on the feature of group rearranged non-zero-digit number,the algorithm has a higher correct rate of scrambling key estimation,more information are leaked from the decrypted image,and a higher-quality decrypted image can be obtained under smaller blocks.