Research On Fragile Watermarking Based On Image Authentication

Digital watermarking technology can embed copyright information that is on behalf of theowner’s identity into the digital products to achieve copyright protection, content authentication andso on. Therefore, the digital image watermarking technology has become a hot topic. According tothe requirements of digital image content authentication, this thesis puts forward two types ofwatermarking algorithms: One is complete fragile watermarking algorithm that is used to imageexact authentication. The other is semi-fragile watermarking algorithm that can distinguish betweencommon signal processing and malicious tamper. The main research work and contributions of thisthesis are summarized as follows:1. The thesis systematically introduces the basic principle, requirements, characteristic andclassification of image authentication watermarking techniques, and analyzes the common attackmethods and evaluation standards of authentication watermarking. Some typical fragilewatermarking algorithms and semi-fragile watermarking algorithms based on space domain andtransform domain are introduced separately.2. According to the advantage of high safety of the watermark generated based on imagefeatures, combining with the characteristics of the luminance, texture and contrast of human visualsystem and fuzzy c-means clustering, the thesis presents a complete fragile watermarking algorithmbased on HVS. The fragile watermark was embedded into the least significant bit in the spacedomain of the image. A number of experiments show that proposed algorithm not only improves thetransparency but also can detect and locate the tampered areas accurately.3. According to the advantage of image edge features and quantitative characteristics, asemi-fragile watermarking algorithm combining with the image edge features and quantization ofcoefficients based on discrete wavelet transform is proposed. The features are extracted from thelow frequency coefficients in wavelet transform domain, using the sensitivity chaos mapping to theinitial value and to embed the watermark by quantizing the wavelet coefficients. Experimentalresults show that the watermarked image produced by the algorithm has good transparency;meanwhile, it can distinguish between malicious tamper and common image processing operationssuch as JPEG compression and adding noise.