Research On Watermark Of Printing Anti-counterfeiting Technology

With the fast development of Internet and the application of digital works, peoplehave enjoyed the convenience and faced the risks of being verified. Digital watermark isan effective way to protect the copyright, which is a mutual way now. With the fastdevelopment of info-tech and high quality image processing equipments, especiallylaser printers, high precision color inkjet and scanners, life has become much easier. Butat the same time, someone can easily verify and fake the certificates, invoices anddocuments. It is of great importance to study an algorithm against printing andscanning.The paper studies on the application of digital watermark in printing security areafrom both theoretical and practical sides. The method has deep theory foundationthrough double random phase modulation encryption holographic technology, Fourierencryption holographic technology, printing technology. Firstly, two digital watermarkalgorithm were proposed, which laid a good basis for printing watermark algorithmdesign. Then the constant characteristics is extracted for analysis, after analysis,anti-printing algorithms were proposed. The main idea of this paper is as follows:1. On the basis of principle of digital watermark and classification and modes,Analysis of the digital watermarking and printing watermarking difference is done tomeet the requirement of printing watermark system.2. A new watermark algorithm was proposed with the analysis of DWT theory.This algorithm is based on human visual characteristics, Intermediate frequencycoefficient through DWT is used to embed watermark, and meaningful binary image isused as watermark. According to different watermark images, the intermediatefrequency coefficient was changed twice to embed watermark in order enhancerobustness.3.Combining double random phase modulation encryption holographic technologywith CIELab color space, DWT with DCT, an encryption holographic watermarkingalgorithm was proposed. Double random phase modulation encryption holographictechnology can ensure the security and blind extraction.4. On the basis of Fourier encryption holographic technology and digitalwatermarking, DWT, a Fourier encryption holographic algorithm based on DWT was proposed. From the experiment results, the embedded watermark can stand normalprinting process, which can be detected after printing once, and the extracted watermarkis fragile after printing twice. This algorithm can stand all basic image processingoperations.5. On the basis of CMYK color space and Fourier encryption holographictechnology and digital watermark theory, a holographic watermarking algorithm basedon CMYK color space was proposed. This algorithm does not transfer the color space,which avoids loss of the watermark information before printing. Symmetricalwatermark is encrypted, due to the Fourier, when decryption, conjugate image and theoriginal watermark image stack with each other, which enhances the definition of thereconstructed watermark.