Research On Image Joint Compression-Encryption Algorithm Based On JPEG2000and Chaos System

With the rapid development of network communication technology, the situation of Internet security problem is becoming more serious. As one of means to acquire information, the mount of digital image data transfer on Internet increasing sharply, the majority of them include significant information as well. Therefore, in order to decrease the storage space of digital image, reduce data transfer bandwidth, improve the security and instantaneity of data which was storage, transmitting and switching in the process, it is necessary to synchronize compression and encryption of image.On the basis of deep research on JPEG2000coding criterion and typical chaos system, a novel image joint compression encryption algorithm was proposed. At first, Euler algorithm was used to calculate the value of continuous Lorenz chaos system. Then, m sequence was introduced to disturb the binary chaos sequence, and regarded the final output sequence as key sequence. Based on further analysis with the adaption realization process and the encryption feasibility of MQ coder, encryption algorithm and key sequence were used to modify the context and decision which were generated by bit plate coding of JPEG2000, which lead to the result of adaptive probability model estimate of MQ coder was changed, so that the output code stream of sub coding process was changed. Therefore, the arithmetic encryption was synchronization realized with the data compression. The fundamental of arithmetic encryption realized by modifying context and decision were elaborated, and the principle of resolution selection encryption was analyzed.Take simulation on the proposed algorithm and the data analysis indicate as follows. From the point of vision quality of reconstruction image to analysis that both contexts modified and decision modified can realize image joint compression encryption, in addition, the proposed algorithm has the same compression efficiency compared with the original algorithm at the same bit ratio. On the perspective of security performance of reconstruction image to analysis that the proposed algorithm has prodigious key space and period can well resist exhaustive attack, great key sensitivity and cipher balance can well resist differential attack, moreover, it has good time efficient of encryption and decryption. Compared with other compression encryption algorithm, the proposed algorithm well balanced the relations between and among image compression efficiency, security performance and the real time of data transmission. From the perspective of resolution selection encryption to analysis that image hierarchical encryption can be realized by assigning different key sequences to different resolution wavelet sub-band coefficients, furthermore, the key sequence of lower resolution error, the PNSR value of reconstruction image will be less,and the vision quality of reconstruction image will be worse.The proposed algorithm can synchronize image compression and encryption, the encrypt operation has little effect on the compression efficiency which improve the security of image data to great extent. Besides, the proposed algorithm has many advantages such as little hardware resource consuming, little calculated amount and high real time. What's more, it can realize image hierarchical encryption according to the requirement of actual circumstance. The proposed algorithm has a good application foreground.