The Research On Digital Watermark Image Authentication Technology

Digital watermarking is an important branch of information hiding technology. Digital multimedia information on copyright protection has been discussed by a lot of papers, while the reality authentication of information content and the integrity authentication of image have developed with the development of network technology in recent years. The eager market demand and the wide application prospects have been attracting many researchers into the fields so that the current information authentication become hot in the field of research. However, the (semi-) fragile watermarking technology is still in the initial stage, and far less mature than robust watermark technology in the results of theoretical and practical aspects. There are still many problems to be studied and explored. In this paper, an important branch of the digital watermark -- a watermark image authentication is mainly discussed. The background, the basic theory and techniques of authentication watermark have been related. Focusing on the vulnerability of fragile watermark and semi-fragile watermark algorithm and comparing their advantages and disadvantages, three certification methods based on them are improved and made.Aiming at positioning accuracy and security of existing spatial fragile watermark algorithms, a fragile watermark algorithm based on a chaos of the fragile for image tamper detection and accurate location is presented. Algorithm divides the original image into 2×2 blocks and calculates image pixel blocks in the high 6-bit gray average (accurate to two decimal places) as the watermark information. The use of binary logistic chaotic sequence of bits embedded watermark to determine the location and encryption, authentication watermarking information will be embedded in each pixel of the lowest effective 2bits bit. Experimental results show that the algorithm could be tampered with the occurrence of complete and accurate positioning detected an effective resistance VQ attack.A watermark information scrambling algorithm based on Arnold's best scrambling algorithm is presented, which scrambles the above spatial watermark algorithm's watermark information, so that the watermark information in the key under the control shows similar uniformly distribution in the white noise characteristics. Tramper detection and similar recovery can be achieved without the original image during image detection certification.According to JPEG compression, a semi-fragile watermark algorithm combining DWT and DCT is presented. Firstly, DWT is used to abstract stable feature of an image and map it as the watermark, which is encripted by a key generated and controlled chaotic sequence. Then, DCT is applied on the original image and the watermark is embeded in DC coefficiencies of DCT. Aftere that, the image containing watermark is produced by IDCT. Experimental results show that the algorithm when appplying to image contend can not only distinguish between normal compression and tampering, but also accurately locate the tamper position to lossy image compression of JPEG with better robustness.