Study Of Digital Watermarking Based On Lifting Wavelet Transform

With rapid development of information technology and computer technology, information security has become the focous of information industry nowdays. As a new style technology of information hiding, digital watermark has incomparable advantages in the copyright protection of digital products, authentication of original data and data detecting, which is becoming a new developing information security technology.Compared with the spatial domain digital watermarking technology, the security and behavior of preventing attack of the transformed domain ones are better, which became the foucus of digital watermarking technology. With the enforcement of the new compression standard of picture and video, the digital watermarking technology based on DWT are becoming the focus of the research of digital watermarking. Howover, the DWT is a kind of float-point wavelet transformation that it cann't precisly reconstruct the original picture. While the wavelet lifting transformation is a kind of wavelet transformation from interger to interger. Then the digital watermarking technology based on it can mitigate the distortion of the reconstructed picture to the maximum.Based on the technology of wavelet lifting transform, the robust watermark algorithm and fragile watermark are researched,respectively.First, the distributing characters of the coeficiency of wavelet are analyzed in domain of wavelet transform. Then combinded with the achievement in the research of HVS, an result is concluded that the effect of the method of inserting the watermark in zhe low-frequency subband is better than the high-frequency ones.Second, by way of Logistic choas mapping, a bindary watermark and a gray image are encrypted, respectively. And the correspongding encryption scheme and dencryption scheme are given also. Moreover, the security and responsibility of the algorithm are analyzed.Thrid, a simple nonblind watermarking algorithm of binday image was given, and the effection of the algorithm,which inserts the watermark in low-frenquency subband, are compared with that in hihg-frequency subband. Besides, the robustness of two algorithm to resist the operation and vicious attack to the images, which contain the watermark, is also researched. The results indicate that the robustness of the low-frequency subband inserting algorithm is better than that of high-frequency. Moreover, a semi-blinding gray image watermarking algorithm, which aimed at RGB color image, is alos given, and the quality of robustness of this scheme is validated by some tests, and can survive JPEG compression, filtering, cutting and so on.Finally, based on RSA cryptographic algorithm and Logistic choas mapping, and combined with the wavelet lifting transform, a fragile watermarking algorithm is given, which only need the deciphering key, the branch parameter and the name of subband which the watermark is embeded in, to exttact and detect the watermark. The result indicate that this algorithm has strong sensitivity to the operation of the images.