基于分数阶傅里叶变换的声呐探测信号鉴别

针对水下声发射源较多,为能准确鉴别敌我声呐发射源问题.利用数字水印技术,结合分数阶傅里叶变换(FRFT)的良好时频特性,提出了基于分数阶傅里叶变换的声呐水印方法,通过在声呐信号的分数阶傅里叶变换域进行数字水印的嵌入,结合声呐信号在分数阶傅里叶变换的系数特性,选择合适的水印位置.利用嵌入前与嵌入后信号的特性自适应设定水印检测阈值,实现对声呐信号的鉴别.通过仿真分析验证了该方法的可行性,在仿真结果中示出该方法在保证具有较高的分辨力,以及较大的水印容量的同时,水印的鲁棒性较好,检测精度得到了进一步的提高.     

一种基于Arnold混沌映射的数字水印技术研究

数字水印技术作为版权保护的重要手段,已得到广泛地研究和应用．提出了一种基于Arnold混沌映射的数字水印技术和水印信息置乱效果评价方法,用Arnold变换对原始水印信号进行置乱,再经过M序列扩频,将处理后水印信号嵌入宿主图片小波域的低频系数中,通过对四组不同条件和嵌入方法的比较,通过实验证明该算法具有良好的稳健性．     

一种基于数字水印的二维条码防伪的方法

针对现有PDF417条码的数字水印嵌入和检测算法比较复杂、水印的嵌入强度不好控制以及对条码打印机和扫描仪的精度要求比较高等问题,提出了一种在PDF417条码的合适边缘嵌入盲水印信息的方法,将二维条码和数字水印技术相结合以提高PDF417二维条码的安全性和保密性.     

基于离散小波变换和人类视觉系统的数字水印算法

通过对人类视觉系统(HVS)的亮度特性、频域特性、图像类型特性的研究,提出一种基于离散小波变换和人类视觉系统数字水印算法,将秘密信息嵌入到小波变换不同的方位系数中.实现了水印信号在图像信息中的嵌入与提取,达到隐藏秘密信息的目的.实践证明该算法能提高水印的不可见性,同时具有很强的鲁棒性.     

混沌映射在彩色图像水印中的应用

提出了一种新的基于混沌理论的彩色图像水印方法.在空域中RGB色彩空间的蓝色信道里嵌入水印以提高水印隐性和鲁棒性.水印的检测同样只在蓝色信道里进行,通过相关性的比较来确定结果.实验结果表明,文中所提出的水印方法速度快、易于实现,具有较高的安全性,并对包括剪裁在内的几何攻击有很好的鲁棒性.     

一种多类多水印方案

通过分析多类多水印的特点，讨论了多类多水印的技术难点，提出一种基于小波系数分块嵌入水印的解决方案，将各类型水印归一化处理，但对每种水印单独制定自适应嵌入技术，实现3种类型7个水印的同时隐藏．仿真实验证明了该方案的有效性．     

Novel Blind Robust Watermarking Based on Chaotic Mixing

This paper proposed a novel blind robust watermarking scheme. Multi-bits watermark is embedded in the chaotic mixed image blocks. Energy of the watermark is spread to all region of the blocks instead of some individual pixels, which entitles the watermark with imperceptibility and high robustness. A class of 1-D Markov chaotic maps is employed to perform image block mixing and watermark encryption ensures security of the system.To prove the validity of this proposed scheme, some objective comparisons with the popular spread spectrum scheme were also presented. The simulation results show that this scheme can survive processing such as high-ratio JPEG compression, Gaussian noise pollution and histogram equalization.     

软判决检测的鲁棒图像水印方案

数字水印技术是现代版权保护的手段之一,而数字水印系统的鲁棒性是其能够起到版权保护作用的必要条件,也是当前的研究热点。本文提出了一种Turbo编码的图像水印的软判决检测算法,在不改变原有的嵌入算法的前提下,只需在接收端采用软判决检测算法就能有效地提高水印系统的鲁棒性。在本文提出的方案中,首先把原始水印信息进行Turbo编码,在图像DFT变换域中,修改两个相同频点系数的大小关系来嵌入经过编码的水印信息。在检测水印时,采取软判决检测算法提取用于Turbo译码的软输入信息,可有效地提高系统的鲁棒性。实验结果表明,软判决检测的比特错误率普遍低于硬判决检测的比特错误率,在高斯噪声情况下,甚至能低0.169。     

Research on anti-counterfeiting quick response 2D barcode techniques based on digital watermark

In order to increase the watermarking capacity and improve the anti-counterfeiting performance of quick response (QR) two-dimensional (2D) barcode based on digital watermarking technique, this paper proposes a kind of graying algorithm for binary image to make transform domain watermarking methods possible. Based on the graying algorithm, the quantization-based watermarking scheme in discrete wavelet transform (DWT) domain is then designed. The experiments show that the proposed watermarking scheme for QR 2D barcode greatly improves anti-counterfeiting performance without loss of any barcode information.     

A New Fragile Watermark for Image

Fragile watermarking is a method to verify the integrity and authenticity of multimedia data. A new fragile watermark for image was proposed, which can be used in image verification applications. The paper first described the above two techniques, some of which will be used in the method. Then it described the embedding and authentication process and also analyzed the method to show how it can survive some attacks. The experimental results show that the proposed method doesn‘t need the watermark or original image on authentication side. It provides more security against attack, and can localize where the temoerinlz has occurred.