Design On The Combined Authentication And Encryption Security System Of Digital Image

In recent years, with the rapid development of science and technology, manydigital products are widely applied to various fields of life. Information security issues,especially the digital image security issues, increasingly attract high attentions of theacademia and business communities. The multimedia digital image security issuesmainly include the integrity and confidentiality of information. They are implementedby the authentication and encryption, respectively. However, in order to ensure thesecurity of system at the same time, these two technologies should be combined to study.The traditional designs simply combine an authentication algorithm with acryptographic algorithm in a certain way. However, these algorithms don’t fullyconsider the features of the digital image including strong correlation between adjacentpixels, high redundancy and the large amount of data, which leads to high timecomplexity and space complexity. Thus, it is difficult to meet the efficiency andreal-time requirements of information security in network era.To remedy the above mentioned demerits, a new security system of digital image,which combines authentication with encryption, is proposed. The main work of thisthesis is as follows:①The related knowledge of digital image is briefly introduced. On this basis, thebasic principle of digital image authentication techniques is outlined, and the indicatorsis given to evaluate the quality of the algorithm. Finally, digital image authenticationtechniques are classified from three different aspects, and the future of their applicationis introduced.②Cryptography, chaos theory as well as digital image encryption technology areoutlined. First of all, cryptography and chaos theory are discussed in detail, and thetheoretical framework and performance evaluation of digital image secure transmissionare summarized. Finally, digital image encryption techniques are classified in manyways.③A new combined authentication and encryption security system of digitalimage, which could protect both the image integrity and confidentiality, is studied indetail. At the sender, firstly, the location watermark of each pixel of the image isgenerated by utilizing pixel-correlation technique, and embedded to the LSB bit of thepixel itself. Then the relation watermark and detection watermark of each partition of the image are calculated, and embedded to the excursion block and the block itself,respectively. Finally, the entire watermarked image is encrypted with chaotic cipherwith variable-parameters. At the receiver, firstly, the image is decrypted with the sameencryption key. Then the extracted and recalculated watermark is compared todetermine whether the image is tampered or not. What’s more, content tamper andwatermark tamper could be separated. If the content has been tampered, then tamperingcould be further localized to a specific pixel by pixel location watermark. Otherwise, theoriginal image could pass the authentication and be completely recovered. This systemnot only could resist known-plaintext and chosen-plaintext attacks, but also could resistquantization and Oracle attacks. In addition, a large number of experimental simulationresults also indicate that the algorithm is feasible and efficient, especially in multimediaapplication requiring both integrity and confidentiality of the original image.Finally, this work is summarized and the future direction is given.