| The problem of the Digital Right Management (DRM) becomes more and more serious. Many governments, academes and enterprises are trying to find good ways to protect different kinds of digital content and build effective DRM systems. The technique that combines cryptography and watermark is a better way to provide a solution to the DRM problem. The DRM technology based on cryptography and watermark is deeply researched in this thesis, including the DRM protecting modes and the DRM protocols, the software obfuscating technique and its integrating with software watermark. The main innovative views in this thesis are the improved cryptography technology, which is used in the protection of software copyright, the improved protecting mode and the improved protocols of the DRM. Main achievements in this thesis are summarized as follows:1. On the basis of published paper, an ID-based provable secure and strong designated verifier signature scheme, a modified strong designated verifier signencryption scheme, and a modified extended aggregate signature scheme based on the supersingular elliptic curve is presented in this thesis. A new provable security watermarking scheme is also presented, which can resist all known existing attacks to the watermark protocols, and also has good capability of correcting error. These schemes are very fit to be used in our mode of DRM and its protocols.2. An ID-based and evolutional password-based conversation key scheme for DRM system is proposed in this thesis. Using evolved passwords and random value means that the same nodes have different passwords, which induces different keys pairs and different conversation keys during every communications. The scheme doesn't depend on any node, uses the ID-based passwords can reduce the computational complexity, so it is practicable for DRM system. 3. A new DRM protecting mode based on cryptography and watermark is proposed under considering actual needs for digital rights entities and security risk. It mainly includes the copyright registration, the embedding watermark, the online business, the authentication and the arbitration, and can provide many kinds of services. The protocols for the mode is also presented, the mode and its protocols can resist many algorithm attacks and protocol attacks, provide good security and practicability. In additional, an improved efficient and anonymous buyer-seller protocol is also proposed.4. We adopt concurrency method, and use the knowledge of the number theory, such as the Legendre symbol and the the congruence equation to construct some families of the opaque predicates that are suit for Java program. After analyzing the shortages of the existing software watermark schemes, An ID-based watermark scheme for Java program is proposed using obfuscation techniques and software watermark. It uses identity to create the watermarks, which are embedded into the opaque predicates after they are encoded. The Java program is obfuscated by taking the opaque predicates with the watermarks as the threads of the Java program, and the watermark is verified by zero-knowledge proof. |
