Research On Group-Oriented Anti-Collusion Fingerprint Algorithm For Important Electronic Document Protection

With the development of the Internet, the requirements for the important electronic documents protection in the intranet have become more and more sophisticated. Information security based on the traditional cryptography means has not met the needs of practical applications. Digital watermarking and digital fingerprinting technology can make personal information associate with specific behaviors, and enhance the controllability of the information. Therefore, researching how these two technologies are used in the intranet for important electronic documents protection has important theoretical and practical value.The article has discussed the necessity and the feasibility of introducing the technology of digital watermarking and digital fingerprinting in protecting important document, as well as some other problems need to be noticed. Based on that, we formulate basic objective and involved content. Elaborated the basic model of digital watermarking, evaluation indicators and attacks against it, at the same time put emphasis on the digital fingerprint technology including fingerprint classification, encoded mode, attacks against fingerprint and fingerprint tracking. And then generalize some problems of the fingerprint tracking.With the design of a digital fingerprint algorithm which based on BIBD block, we have analyzed the advantages and disadvantages of two important encoding which are orthogonal code and the BIBD code. Based on that, designed an orthogonal code that are based on BIBD block and combined their respective strengths. After analyzing the behavior of collusive users in the intranet fully, the algorithm has divided the high probability of collusion into a group and the low probability of collusion into another. In addition, the algorithm has used a concatenated code encoding. Internal code is used the orthogonal code based on BIBD block, and external code use a kind of widely used error correcting code, that is RS code. The article has given the encoding and decoding algorithm associate with digital fingerprint algorithm, analyzed the performance of the algorithm including the algorithm's time complexity and space complexity, calculated the length of algorithm code and compared with two classical coding algorithms. The algorithm has been simulated in the Matlab environment. The experiments mainly validate from the spatial domain and frequency domain. The action of attack mainly inspect the AND attack and the random choice attack.The result shows that, for AND attack the algorithm is able to track all collusive users, for the random attack is able to track multiple collusive users in most cases, for only a small number of cases can just trace to one.