Reversible Data Hiding For VQ-compressed Image In Encrypted Domain

Data hiding technology is an important part of information security.Based on this technology,secret data can be embedded in multimedia signals and then extracted from the marked signals for various uses.However,the original signal is unavoidably changed in most data hiding methods.Especially with the rapid development of cloud services,data needs to be encrypted before uploading it to third parties.Therefore,data hiding in encrypted domain has become important.Larger storage space and loans are required in the process of multimedia signal transmission.In order to improve the transmission performance,the technology for data compression is used?In this paper,the research background,the status of data hiding technology and reversible data hiding technology will be introduced.Vector quantization is a typical data compression method,which has been widely used in image and audio signals.There are many excellent data hiding schemes for VQ compressed images,however,little research has been done in encrypted domain.Hence,this paper mainly studies the data hiding technology of encrypted domain based on VQ compressed image.We propose two schemes,which are the data hiding algorithm by using chessboard method to modify VQ codebook in encryption domain and the reversible data hiding algorithm based on VQ index grouping for high-capacity in encryption domain.We also design the statistic experiment to test the algorithm performance.The experimental results show that the proposed algorithms have better data hiding performance and better direct decryption image PSNR.The main contributions of the paper are as follows.(1)A proposed data hiding scheme by using chessboard method to modify VQcodebook in encryption domainIn this scheme,the codebook is firstly rearranged according to the Euclidean distance between the codewords,and the rearranged codebooks can form several codeword pairs.In each code word pair,two code words are adjacent and have large difference in the mean value.Next,the index table and the newly generated codebook are encrypted with modulo operation and stream key,respectively.In a third party,the data hider can modify the index value at a specified position in the index table with the checkerboard layout,and use an addition operation to change the index to another value in the code word pair,then reversibly embed the data bits in the index table.The receiver first uses the key to decrypt the index table and codebook respectively.After decryption,the result of the addition operation of embedding process still exists.However,additional data can be successfully extracted and the image content can be restored according to the spatial continuity of natural images.In the experiment part,the performance of reversibility will be verified.Four typical images and four codebooks of different sizes will be selected to verify that this scheme is good at embedding large amount of data.(2)A reversible data hiding scheme based on VQ index grouping for high-capacityin encrypted domainContent owners need to be encrypted VQ compressed images by encrypting the index table in a permuted manner,and adding a cryptographic book with a stream key.The content owner sends the encrypted data to the cloud.After the data hider gets the encrypted data,he sorts them according to the number of times the index appears,and organizes the HL index group.Each HL group must contain an index value with a high number of occurrences and at least one index value with a low number of occurrences.The fixed-length additional data will be embedded by changing some high-frequency indexes in the index table.In order to ensure the reversible recovery of the data,some side information needs to be recorded.Data extraction and image recovery can be performed on the receiving side.Experimental results show that the scheme is completely reversible.The performance of the scheme is analyzed by adjusting different parameters,such as different images,different codebook sizes,and different thresholds.According to the comparison results between the scheme proposed in this paper and other literatures,the proposed scheme has a high embedding rate and is a reliable reversible data hiding scheme in the encrypted domain.In conclusion,the proposed methods in this paper provide some new ideas to the existing technology of information hiding of VQ compressed images in encrypted domain,and has good performance in field of scientific research.