| Digital watermarking is a well-developing information security technique, which can be combined with traditional cryptology to enhance controllability and security of information. To achieve the requirement, it is important and practical to research in the following fields, such as digital fingerprint coding and detects algorithm; asymmetrical digital fingerprint protocol; digital watermarking infrastructure for key information protection; identify e-documents based on watermarking technique.Theory and technique base of Cryptology, digital watermark and digital fingerprint are discussed. The point of cryptology and digital watermark can be combined to enhance security of information is proposed. The relationship between digital fingerprint and digital watermark is analyzed and the concepts of them are differentiated.CDRC(Coding and Detection algorithm based on Random Code)which is an effective and elegant anti collusion fingerprint coding and detecting algorithm is proposed. CDRC, based on embed assumption, utilizes random codes to form digital fingerprints, evaluated the correlation between user fingerprint and collusion fingerprint by hamming distance. The algorithm is described and analyzed deeply, including implementation, safety, efficiency and fault probability. Also CDRC is compared with other algorithms of the same kind.Several well-known digital watermark protocols are studied. Considering the model of community exchange and fingerprint application, PDWP(Practical Digital Watermarking Protocol) is proposed. It is seamlessly integrated with PKI-CA system by adding watermarking functions to CA of PKI-CA system to form W&CA. PDWP also provided digital fingerprint certificate which is confidential to users to fulfill asymmetric attribute of digital fingerprint protocol. With reference to PKI-CA, the concept of DWI ( Digital Watermarking Infrastructure)is formed. DWI marked network user activities by adding fingerprint attribute, in the form of generating digital fingerprint certificates. The structure and entities of DWI are defined; relevant general tasks between these entities are described; then DWI is compared and analyzed with PKI and IMPRIMATUR.A generally suitable framework for watermarking application is proposed base on hierarchy. It is not only suitable for identity e-documents but also suitable for other kinds of digital watermarking application. It was composed by three layers: driver layer, adapter layer and application layer. Then based on the techniques of layered watermarking, a scheme of identity e-documents is proposed based on digital watermarking technique. Also, the identity formats of confidential e-documents and the way to use it are discussed.A prototype for protection of e-documents of a mini or medium sized classified net system is actualized in view of the systematical requirement, DWI, digital fingerprint codec algorithm, asymmetrical fingerprint protocol and e-documents identification solution. Come with PKI and PMI, this prototype showed the process of dealing with important e-document, meanwhile the function and security of the prototype are analyzed.According to the research related to digital fingerprint and watermark, progress in both theoretical and practical ways are made and formed fundamental achievement for further development in application research.
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