Watermarking For Color Image Authentication

Replication, storage and processing of digital multimedia information become more and more convenient with the rapid development of computer and network technology, So the problem of how to ensure the authenticity and integrity of the digital multimedia information is urgent to treat, the rise and development of image authentication technology provides a good idea and method to solve the problem.There are mainly two image authentication technologies currently, fragile image authentication watermarking and semi-fragile watermarking. The former is mainly used for precise image authentication, it's vulnerable for all image processing operation, and the latter is mainly used for detection of image tampering, They have the following disadvantages:1) Most of the original images are grayscale, the applications are restricted; 2) fragile watermarking technology is not precise enough to locate the tamper places, and low in Security; 3) It is not robust enough and lack of adequate security for semi-fragile watermarking to handle many common image processing operations.The paper analysis the relevant research deeply, based on the lack of current image authentication technology, do the research of the color image watermarking algorithm in depth. The major work and innovation are as follows:1)A fragile watermarking algorithm based on chaotic system is proposed. This algorithm modulating watermarking combine the excellent properties of Logistic chaotic systems with the characteristics of color image. Algorithm calculate the luminance of each block to decide the depth and the length of watermarking, for each pixel, an initial value is determined based on its prominent chrominance value, the position index, and the image protection key, can detect the tamper position exactly and own high ability to stand VQ attack, it own higher security either.2)A semi-fragile watermarking algorithm based on Wavelet theory is proposed. As the characteristic of human visual, a luminance-chrominance model space (YCbCr color space) was chose, the luminance component Y is decomposed by L+1 level dwt decomposition, and use the wavelet coefficients matrix of Y as original watermark signal, using the generated binary chaotic sequence by Logistic chaotic system and the real masking matrix modulate binary watermark information, finally, luminance component Y and chrominance component Cb and Cr are decomposed by L level dwt decomposition, and the watermark are embedded into color component Y, Cb and Cr using technique of block quantization. Experiments show that the algorithm in high safety and transparency, and can tell the difference from conventional image processing and malicious content tampering.Finally, the work is summarized and the future direction of digital watermarking are pointed out.