Digital Signature Applied Research

As a kind of technology, cryptography has a long history, but as a science, it is still very young. Signature is a focus of modern cryptography. The popularity of Internet and the improvement of stream media compress technology make digital products such as digital works, images, video, music and games etc rapidly spread online. Because digital contents can be copied, tampered and spread easily, if no suitable technologies are applied to protect the copy right of digital products, illegal copying, tampering and spreading of digital products will hurt the right of originator and result in great loss of the providers. Digital rights management (DRM) is a core technology for protecting digital products and digital intellectual property.Existing DRM technologies are based on information hiding, but not on cryp-tography. Without solid foundation, existing DRM technologies cannot properly protect the security and may cause some potential danger. Furthermore, most DRM neglect the protection of users' privacy. Combining signature and DRM technology, this paper successfully eliminates the hidden danger of existing DRM technologies with following work.(1)To deal with the problems with existing online electronic answer sheet evalu-ation system, this paper proposed a dual signature scheme to protect the electronic answer sheet. The scheme can protect the integrity, authenticity and examinees' privacy. During the review process, the reviewer can associate the score to cor-responding integral answer sheet without knowing examinees'name, realizing the sealing test marking function.(2)Existing DRM systems focus on protecting the illegal copying of digital con-tent to guarantee the interests of content providers without protecting the users' anonymity. This paper analyzed the characteristics of existing group signature and proposed, based on group signature, an improved DRM system which can protect the users' anonymity. The system described in this paper can guarantee the anonymity of legal users, meanwhile can reveal the identity of illegal users.(3)Finally, based on the analysis of existing digital rights management system, aiming at the structural features of digital rights management system, a digital rights management system control model is proposed. This model can be used to dynamically distritbute the permission right to prevent resources from being illegally copied.