Digital Watermarking For Forgery Detection In Printed Materials

With the development of information technology, the high accuracy color ink-jet laser printer and high precision scanners are widely used, the manipulation and falsification of presswork such as bill, certificates, currency and product outer package is easier than before. Therefore, we need a new presswork anti-counterfeiting technology to solve the problem of manipulation and falsification.Resisting attack on image during the process of print and scan is the key to print digital watermarking technology. This paper firstly introduces the working principle and mechanical characteristics of printer and scanner, analyses the influence of print and scan to the picture quality, and on this basis, to research the presswork anti-counterfeiting watermarking algorithm.Through further study on the digital watermarking, wavelet analysis theory, chaotic scrambling theory and fuzzy integral integration theory, this paper puts forward a kind of wavelet domain presswork digital watermarking algorithm based on fuzzy integral fusion, which has good robustness, and can resist the attack during the process of print and scan. Hashing algorithm has good safety and scrambling effect, therefore, we firstly encrypt the watermark image through the chaos of scrambling, which will take the initial value of chaotic sequence as the scrambling key; Then we carry out wavelet transform to the carrier image, choose to embed watermark image encryption in low-frequency coefficients and high frequency coefficients of wavelet transform domain; carry out wavelet transform to the images to be detected when extracting watermark; compare the wavelet low-frequency coefficients and high frequency coefficients of original watermark image and images to be detected and get watermark information of different components, get the ultimate encryption watermark through fuzzy integral fusion strategy, and finally, using the chaotic scrambling watermark declassified algorithm to restore the watermark information.At the end of this paper, we prospect the future research direction of the digital watermarking technique, and look forward to more and more watermarking algorithms.