A Double Watermarking Algorithm Based On Discrete Wavelet Transform

The rapid development and wide application of computer and network technology have made obtaining of digital multimedia products easier and faster while the invalid copy, forgery, tamper of digital multimedia products also have become more easier. Traditional encryption techniques can't protect digital data anymore. Digital watermarking is proposed as another effective solution to protect both the digital production and the profit of its owner.A novel double digital watermarking scheme with self-adaptive quantization based on wavelet transform for copyright protection and integrality authentication is proposed. Two kinds of digital watermarking, robust watermarking and semi-fragile watermarking, are embedded into a digital image using multi-resolution of wavelet transform. The double digital watermarking scheme is precise to tamper localization. The watermark is born from the original image. First, the copyright protection watermark is built by correlation analysis and bits extend of content-based watermark. The correlation analysis can achieve the lowest distortion of the watermark and information redundancy by carrying one bit information with several bits. The watermark with more redundancy has stronger capability for resisting attack. Then, copyright protection watermark is transformed into disorder so the attacker can't unscramble the watermark and the watermark system become more safely. The disorder transform, dispersing the wrong bits, can show the watermark as a better vision and enhance its robustness. The authentication watermark is built by hash transforming content-based watermark. Thus, the authentication watermark will be very sensitive to tamper owe to the character of hash function.A novel expression of texture feature is defined and the quantized length is adaptively decided by the texture feature. Then a quantizing method with good transparence and robustness, using to embed watermark, is proposed. Pretreated protection watermark is embedded into wavelet median-high frequency by block quantization with neighbor information. And the authentication is embedded by singular coefficient quantization.Experiment demonstrates that the double watermarks embedded by proposed algorithm are imperceptible. The protection watermark is robust to general image process attack and spiteful tamper attack, such as noise adding, JPEG compression, filtering, rotating, contrast decreasing, cut and cut-replace attack while the authentication watermark is robust to appropriate compress, little noise adding, filter attacks, and sensitive to spiteful tamper such as cut and cut-replace. The authentication watermark is semi-fragile and precise to tamper localization. In a word, the double watermarking algorithm is good at copyright protection and content authentication simultaneously.