Dual Digital Watermark Algorithm Based On Logistic Chaotic Map

The advancement of network and multimedia technologies has been gradually making the multimedia data an important source from which people can acquire information. How to efficiently and safely protect such information is now being the hotspot in current studies. As one of the important branches of information hiding technology, digital watermarking is also an important measure to protect the intellectual property. By embedding the confidential information, known as watermark into the original information, its proprietary and integrity can be verified in order to protect against illegal copying or altering of the digital product. This article emphasizes on the algorithm of dual digital watermark.From initially the spatial domain digital watermarking algorithm to the transform domain digital watermarking algorithm and to subsequently the NEC algorithm and the biological mode algorithm, the robustness of algorithm has been enhanced in some aspects. However, it is still impossible to protect the information against comprehensive attack yet. Therefore, several researches on such as"Re-embedment","Dual Detection"and"Multiple-Embedment"emerged under this condition. Although these researches differ in their names, but they have similar concepts that can be generally understood as that several independent but complementary digital watermark sub-algorithms are integrated in order to make up for defects of each sub-algorithm with no effects on the invisibility of watermark, so that they can protect again attack jointly and result in by far better performance of watermark algorithm than that of embedment in single manner.At the beginning of this article, the background and present situation of studies on digital watermark, basic concept, classification and application of watermark, as well as research trends in the world are introduced. Some key points such as transform domain and encryption involved in image digital watermark algorithm are also discussed in detail. On the basis of the study and analysis on current watermark algorithms, a dual digital image watermark algorithm based on Logistic chaotic map is provided in this article to improve the robustness of attack resistance of most watermark algorithms, which have been embedded in only one watermark signal. The proposed algorithm uses bi-value image that has been chaotically encrypted as the watermark information. These two values are separately embedded into the direct current factor and high frequency factor. The software Matlab is used to actualize the concept. Through a large number of test data and result analysis, it has been indicated that the requirement of invisibility of watermark can be well met by this algorithm and the embedded watermark shows a good robustness against common image processing methods such as JPEG compression, histogram equalization, slice, noise, mid-value filtration and sharpening as well as noise interference.