Research And Implementation Of Image Encryption And Copyright Protection

With the widely use of digital images, the problems of their security become more and more extrusive. The image encryption and digital watermarking which are thought as the powerful tools to protect digital images have been researched widely. The security of digital images contains image encryption, digital fingerprint, image authentication and copyright protection etc. Image encryption and copyright protection are researched in this thesis. They involve traditional data encryption, chaotic encryption and robust digital watermarking algorithms.In some cases, the images with digital watermarking need to be protected by encryption in order to supervise whether the legal receivers use images legally or not. But recently image encryption and digital watermarking algorithms are researched separately. Or the image encryption is introduced to digital watermarking algorithms, but the encryption is just to scramble the original images and watermarks whose security is low. These researches can not solve the problems above.In this thesis, the main works are as follows:(1) The advantages and disadvantages of AES and chaotic used in image encryption are researched, and an algorithm of image encryption is proposed. We called it RRAES_ICat for short. RRAES_ICat combines the round-reduced AES with the chaotic encryption. The results of experiments show that it not only has good performance of encryption and high time efficiency but also can resist shearing attack. This algorithm is practical.(2) An algorithm of digital watermarking is proposed. It combines LDPC and image scrambling technology. The experiments indicate that this algorithm can increase the robustness of digital watermarking and can resist many attacks such as Gaussian noise attack, salt-pepper noise attack, JPEG compression and so on.(3) The digital watermarking algorithm shown in (2) is combined with RRAES_ICat, then an algorithm which is called the copyright protection of confidential images is proposed. The experiments indicate that this algorithm not only holds the advantages of a digital watermarking algorithm based on LDPC and scrambling technology but also holds the advantages of RRAES_ICat. It is more practical.(4) Using the copyright protection of confidential images, a protocol named Plug-in-based Overlay Multicast Watermarking Protocol is designed. It is called POMWP for short. POMWP is independent of place, just need to send one copy of data and can be used in any platform of overlay multicast. It can protect images of multicast effectively.