The Document Issued System Based On Watermark

In this article ,I mainly probes digital image watermark technology about documents issued system. The digital watermark technology is one kind of effective digital product copyright protection and the data security maintenance technology which appears in the recent ten years. It has overcome the problem that content encrypted in the traditional cryptology technology is no longer safe after it has been deciphered and breaked through, thus as the intellectual property rights protection and the digital multimedia anti-counterfeit effective method, digital watermark technology is obtaining extensive research and the application. Digital watermark technology verifies ownership or integrality of this data byimbedding secret information in initial data - Watermark , by which it resist the act of imitating , denial , distorting etc. during the course of the the official document issued.This thesis described relevant theories of the digital watermark at first, on this basis, indroduced watermark imbedded of mainstream algorithm at present, put forth a self-adaptation blind watermark algorithm based on DC combined AC low frequency and sub-low frequency. This algorithm adopts two value image as the watermark, utilizes human vision shelter characteristics and the lamination characteristics of the image , splits the carrier I of original image into K 8* 8 DCT blocks not covering each other, and according to different lamination characteristics of block, imbeds the watermark signal in DC weight and AC low frequency and coefficient of low frequency separately, thus by which the watermark have the good no observability and have increased the embedding capacity of the watermark;This algorithm carry on Tent-map Chaos system put encrypting to two value watermark image arbitrarily at random before the watermark embedded, have already prevented the early digital watermark from drawback of adopting the false random array (such as M- array ) or one gauss of noises as the watermark to embed, measuring algorithms can only provide the result with the watermark or not, can't meet the the requirement for copyright protection , have improved security of the meaningful watermark and anti-interference ability, the ones that have strengthened practicability , security and drawn are ocular . The watermark has utilized well HVS characteristic in the course of the imbedding, and realized the watermark is imbedded adaptivly, thus the one that has guaranteed the watermark can not be seen , prevent the picture from appearing on an block effecting.This thesis uses a large number of experiments to test feasibility and accuracy of this algorithm, the experimental result indicates the watermark have well resisting rotates, resists noise and JPEG compresses ability , have a better getting sane too to some other common image process (such as low-pass Gassian filter , under median filtering , translation , sharppening , cropping etc.), leak alert rate and empty alert rate is zero, watermark measure result is good.In addition experiment indicate this algorithm applause very kind result to embedding and detection of 24 real color image, have stronger practicability in the official document issued system.This text has been designed and realized a self-adaptation blind watermark imbedding and detection system based on DCT land DC weight combined with AC low frequency and sub-low frequency, and has imbedded it into the official document issued system this text design and develop jointly use with the visit control technology , fire wall technology in this system, have fullyguaranteed the security that the official document is issued.