Research On Semi-fragile Watermarking Algorithm Based On Image Characteristics

The information media can be easily taken, spread, edited that threats thesecurity and integrity authentication of the information media. So, more and morepeople focus on the way to ensure the integrity authentication of the digital media. Atthe same time, semi-fragile watermark has a wide range of applications inauthentication of the digital media because it has double merit of the robustwatermark and fragile watermark so it is promising for authentication applications.As is known, semi-fragile watermark research is not mature yet, with the basicrequirements of that the carrier image can be reliably detected tampering operations,and semi-fragile watermark also need to general routine operating robustness. Manyresearchers pay attention on edge feature for its stable. This paper stands on the basisof edge character, considers using only the outline of edge character and tracking,then puts chain code feature as watermark. Just because chain code acquires on thebasis of edge character, on this condition, this watermark also has semi-fragile. Themajor works done in this article are as follows:First, a quantitative semi-fragile watermarking algorithm based on chain code inspatial domain is proposed. Ground on this method, the original carriers image isdivided into eight multiply eight blocks, then each block is quantized respectively; inthe meantime, two bits watermark information are embedded into each eight multiplyeight blocks according to the parity of coordinates sum. The experimental resultsshow that the algorithm embeds large amount of information, distinguishesconventional attacks and malicious attacks better and locates areas where image beingtampered accurately, but sensitive to the compression operation.Second, an integer lifting wavelet transform semi-fragile digital watermarkingalgorithm based on error correcting code is proposed. The method leads up BCH errorcorrecting code, and then encodes watermark information by BCH error correctingcode, in order to enhance the security of watermark, chaotic scrambling is used. Afterthis, embeds watermark information through relations between adjacent coefficients of HL2decomposed two layers by wavelet. The experimental results show that themethod not only has a good resistance to JPEG compression, but also pinpoints areasbeing tampered; because of the introduction of the BCH error correcting code, theaccuracy of watermark extraction becomes higher.The first method in this paper first has good properties for common conventionalattack, especially for salt&pepper noise and shears attacks. But works in spatialdomain, for this reason, it is sensitive to resist JPEG compression, so the second kindof algorithm is proposed. Wavelet transform can achieve better resistance to JPEGcompression. BCH code is introduced into the integer lifting wavelet to improve therobustness of the semi-fragile watermarking and the integer lifting wavelet canshorten the time of computing, avoiding the trouble on non-integral wavelet processthe fractional parts. The experimental results show that the algorithm meets the basicrequirements of semi-fragile watermark, achieves the expected effect.