Research On JPEG Image Encryption

As the network bandwidth continues to increase and the cost decreases gradually,more and more people transfer images to pulic cloud servers for storage.How to protect the privacy and security of the images during transmission and storage is one of the key issues that needs to be solved in cloud storage.Image encryption is a common technique for protecting the privacy and security of important images.Since JPEG is one of the most widely used image file formats,research on JPEG image encryption has recived widespread attention from researchers.Through the theoretical analysis and a large number of experimental studies on the existing JPEG image encryption technology,this paper summarizes the problems existing in various encryption operations.The main problems are: easy for sketch attack and known plaintext attack;file size increases seriously in encrypted images;poor format compatibility of encrypted images with the JPEG standard;the need for re-entropy encoding during the generation of encrypted images.This paper proposes a JPEG image encryption algorithm based on bitstream,which effectively overcomes various defects of existing literature algorithms.The proposed algorithm includes four encryption operations,which are permutation of consecutive quantized DC codes with the same sign;iterative grouping and swapping of quantized DC codes;permutation of quantized AC codes within the same run length and permutation of MCUs excluding quantized DC codes.Moreover,in order to defeat known plaintext attack,this paper proposes an adaptive encryption key construction method,which is based on image content.In order to demonstrate the superiority of the proposed encryption algorithm,the theoretical analysis and a large number of comparative experimental results are given in this paper.It can be seen from the experimental results that the proposed encryption algorithm is superior to the latest research results in terms of file size of encrypted images,format compatibility with the JPEG standard,theoretical security,and so on.