Study On JPEG2000 Digital Image Encryption Algorithm Based On Chaotic Cryptography

In recent years, with the rapid development of network communication technology, multimedia information as an important carrier of information, is transmitted and exchanged more and more frequently. However, with Internet security issues highlighted, the security and confidentiality of multimedia information especially the image information which is widespread used have become increasingly important. JPEG and JPEG2000 are two important image compression standards extensively used at present. However, JPEG2000, based on DWT, enjoys more advantages and is bound to gradually replace JPEG, becoming the principal. Therefore, the study of digital image encryption algorithm based on JPEG2000 is particularly essential. Under this background, and utilizing the superiority of chaotic cryptography, the thesis just does some studies on JPEG2000 digital image encryption algorithm based on chaotic cryptography.This thesis introduces some basic knowledge and relevant theory about Cryptology, digital image encryption, and chaos theory at first. Then it mainly analyses the first part of JPEG2000, namely, Baseline Mode of JPEG2000, the core coding system.After that, a new image encryption algorithm is proposed by integrating chaotic cryptography with JPEG2000. First and foremost, a matrix scrambling algorithm based on the chaotic system is designed which with excellent performance. Given the DWT, the kernel of JPEG2000, it is used to scramble and encrypt the wavelet coefficient matrix generated by image DWT in the digital image encryption algorithm.As most important image information after DWT is concentrated upon the part of the lowest approximation coefficient, the algorithm is designed only to scramble the lowest approximation coefficient matrix for encryption. Therefore, the algorithm, overcoming some shortcomings which existing in preceding image encryption algorithm based on JPEG2000 skillfully, well comebines the encryption, decryption with image coding and decoding, thus making great improvement over JPEG2000 system.Finally, experiments are implemented to testify and analyse the feasibility and superiority of the algorithm, and the results prove that the algorithm is characterized by high complexity, good performance of security and encoding efficiency, without decreasing the image compression ratio remarkably.