Research On Hybrid Watermarking Resilient Against Copy Attack And Authenticating Legitimate Customer

Most of the watermarking applications use either of two kinds watermarking robust watermarking or fragile watermarking. The two most important applications copyright protection and content authentication one uses robust watermarking and the other uses fragile watermarking. In this paper, we try to use both kind of watermarking to build a hybrid watermarking, which uses robust watermarking to protect copyright and uses fragile watermarking to authenticate legitimate costumer and uses fragile watermarking to help copyright watermarking to combat copy attack.In order to realize such a watermarking, three jobs were finished in this paper: 1. A rotation, scaling, translation resilient watermarking algorithm was designed. In the method, log-polar transformation is used to eliminate the effect of scaling and translation because its invariance to scaling and translation. In the same time, log-polar is also used to clear the effect of rotation with the help of exhaustive search method. Experiments show it works well. 2. A semi-fragile watermarking based imagines · contents was designed. In this method, authentication sequences are derived from DCT coefficients and then embedded in DWT coefficients by quantization. Experiment results show the watermarking is robust against JPEG compression, medium filtering and adding Gauss noises but fragile to replacement attack. 3. An owner-customer watermarking protocol was improved. Owner-customer watermarking protocol has the ability to authenticate legitimate customer. After improved, it runs fast and can prevent legitimate costumer from leaking his secrets that will damage owner · s rights. Analyzing proves the goal was reached.