Research On Some Problems Of Copyright Protection For Optical Disc System

With the development of digital multimedia technology, digital rights management has become a pressing concern for the digital content business. With the widespread applications of optical disc in China, copyright protection of multimedia content in optical disc system being sold is a key problem to be solved. The thesis studies some problems of copyright protection for optical disc system through three main respects: digital watermark, digital video encryption, key management for stateless receivers.As a new effective technological means to the copyright protection for copy tracing, the digital watermarking technology has already become a popular topic in the field of digital copyright protection. First, this thesis presents a new robust watermarking scheme using GRAY code and chaotic encryption for color image. A binary watermark image is permutated using sequence numbers generated by a secret key in a spatiotemporal chaos system. Then, the binary image watermark as a unit was encoded by Gray code, and then adaptively embedded into low frequency components of the original color image's blue channel in discrete cosine transform domain. Second, an improved robust blind watermarking scheme using chaotic encryption for color image is proposed. Third, these watermarking schemes have some technical limitation in robustness against geometric attacks, especially in robustness against global affine transformation, such as rotation, scaling and translation. Because these desynchronization attacks, which induce synchronization errors between the original and the extracted watermark during the detection process, are very difficult to tackle, this thesis proposes a new robust watermarking extract scheme for color image using scale invariant features transform (SIFT) image correction. Experimental results show that the proposed scheme is robust and secure against a wide range of image processing operations such as global affine transformation, filtering and lossy compression. Fourth, the same method that watermarking extract scheme for color image using scale invariant features transform (SIFT) image correction is used to improve another watermarking detected algorithm for color image based on a block probability in spatial domain.Although traditional text encryption approaches can be used to encrypt video data, it has many disadvantages in encrypting mass data at a high real time capability in multimedia application. We must develop a new way to solve the problem of digital video encryption and decipher. Then the selective encryption algorithm becomes the new hotspot of video encryption. The key to develop a video encryption algorithm to reach the real-time requirement and security quality is to make a good balance between security and the excessive cost of the encryption arithmetic operation. The security quality and the operation time of the algorithm will fall if we reduce the complexity of the encryption; conversely, the security quality and the operation time will increase with the decrease of the complexity of the algorithm. A new grade method for video security quality is proposed, and it distinguishes four ranks: important, sub important, common and non requisite. Then a two-way selective encryption algorithm (TWVEA) for MPEG-4 AVC video based on this video security grade method is proposed to compromise the security and speed in the process of encryption. TWVEA improves VEA algorithm and adopts key video data to encrypt during the encoding progress to reduce the excessive operation spending; And three different encryption algorithm encrypt the video data in different security level. These encryption methods include AES, VEA and improved VEA, which are used to encrypt the three areas in one image of video data. This selective encryption of MPEG video streams reduces the required data of encryption, saves in complexity and facilitates new system functionality. After that, another fast selective encryption algorithm named CA-AES-Seal is proposed. It's a new algorithm that combines AES encryption method and Seal encryption method. To make a trade-off between security and encryption cost, AES method is used to protect the core key video data to receive high security quality and Seal method is used to encrypt the sub important video data to realize fast encryption algorithm. Finally, the video encryption scheme named RVEA, which is based on the MPEG-2 video files, is analyzed. And the new grade method for video security quality is found to further can enhance security of RVEA. Both comparative analysis of computing overhead of these video encryption schemes are given.When a legitimate receiver with its initial set-up can obtain the current group session key only from the current transmission without the history of past transmissions, it is named a stateless receiver. Broadcast encryption schemes are one-to-many communication methods in which a message sender can broadcast an encrypted data to a group of users over an insecure channel so that only legitimate receivers can decrypt it. And how to efficiently exclude illegal (revoked) users from a privileged set is the task of the stateless broadcast encryption schemes. So the stateless broadcast encryption schemes need to ensure that only legal users decrypt an encrypted broadcast message. By studying the development trend of broadcast encryption schemes at home and abroad, first of all this thesis introduces the Subset-Cover algorithm framework, and analyzes the complete subset algorithm and Subset-Difference algorithm, focusing on analysis of the advantages and disadvantages of these algorithms. On this basis, a new Layer-Chain key management method is proposed, and the Layer-Chain key management method is described in detail. The comparison of the stateless broadcast encryption schemes shows that the Layer-Chain key management method has a reasonably low user storage and computation overhead.Then, an optical disc copyright protection system framework is given in detail, and the workflow of the safety key management processes shows that video encryption algorithm and Layer-Chain key management method are suitable for the optical disc copyright protection system. Finally a new copy tracing scheme based on video watermark is proposed, which further improves the entire optical disc copyright protection system.