An image rectification scheme and its applications in RST invariant digital image watermarking

This paper presents an image rectification scheme that can be used by any image watermarking algorithm to provide robustness against rotation, scaling and translation (RST) transformations. Rotation and scaling transformations in the spatial domain result in cyclically translational shifts in the log-polar mapping (LPM) of the magnitude of the Fourier transform spectrum of an image. We cut a small block from the LPM domain as a matching template. A new filtering method is proposed to compute the cross-correlation between this template and the magnitude of the LPM of the image having undergone RST transformations to detect the rotation and scaling parameters. We employ the same strategy in the spatial domain to detect the translational parameters in the spatial domain. The scheme can also be used to detect image flipping. The cost of the templates is low and the templates can even be compressed. The detection accuracy for rotation, scaling and translation is also presented. We compare the matching results for the different filters and their performance by the three criteria: signal-to-noise ratio (SNR), peak-to-correlation energy (PCE), and Horner efficiency. We demonstrate that our phase-only filtering method is the only one that can be used in the LPM domain. We also introduce three applications for this rectification scheme and give their experimental results.

基于独立分量分析的小波域数字图像水印算法

提出了一种鲁棒数字图像水印算法。水印生成过程对原始水印进行转换、置乱和扩展等处理;水印嵌入过程将水印嵌入在原始图像小波域的逼近子图,嵌入的强度由噪声可见性函数自适应决定。水印提取过程不需要任何原始图像和原始水印的信息,采用独立分量分析实现对水印信号的盲提取。实验结果证实对于水印基准测试软件Checkmark的各种攻击,该算法具有较强的鲁棒性。     

灰度图像水印的自适应二维数字水印算法

本文提出了一种采用可视灰度图像作为水印信号,根据人类视觉掩体特性进行分类,并结合系数自身的特点,通过修改DCT域中低频和次低频系数来嵌入不同强度水印的算法。实验结果表明,应用所提出的算法实现的水印对常见图像处理和噪声干扰具有很好的稳健性。     

A novel approach to digital image watermarking based on a generalized secret sharing scheme

In the digital image watermarking community, the problem of joint ownership has not been adequately addressed. This paper proposes a novel algorithm that makes use of a generalized secret sharing scheme in cryptography to address this problem. Given that multiple owners create an image jointly, distinct keys are given to only an authorized group of owners so that only when all the members in the group present their keys can the ownership of the image be verified. Any owner alone cannot verify the image ownership. In addition, experimental results show that the proposed algorithm has the desired properties such as invisibility, reliable detection, and robustness against a wide range of image-processing operations.     

A new robust and secure digital image watermarking scheme based on the integer wavelet transform and singular value decomposition

In this paper, a new robust and secure digital image watermarking scheme that can be used for copyright protection is proposed. The scheme uses the integer wavelet transform (IWT) and singular value decomposition (SVD). The grey image watermark pixels values are embedded directly into the singular values of the 1-level IWT decomposed sub-bands. Experimental results demonstrate the effectiveness of the proposed scheme in terms of robustness, imperceptibility and capacity due to the IWT and SVD properties. A challenge due to the false positive problem which may be faced by most of SVD-based watermarking schemes has been solved in this work by adopting a digital signature into the watermarked image. The proposed digital signature mechanism is applied to generate and embed a digital signature after embedding the watermarks; the ownership is then authenticated before extracting watermarks. Thus, the proposed scheme achieved the security issue where the false positive problem is solved, in addition to that, the scheme is considered as a blind scheme. A computer simulation is used to verify the feasibility of the proposed scheme and its robustness against various types of attacks and to compare it with some previous schemes. Furthermore, the statistical Wilcoxon signed rank test is employed to certify the effectiveness of the proposed scheme.     

用于图像认证的数字水印技术综述

随着网络技术和媒体信息数字化的飞速发展,用于图像认证的数字水印技术成为目前研究的热点。主要阐述了当前用于认证的数字图像水印技术的特征、认证系统框架,详细讨论了脆弱水印和半脆弱水印的算法和研究现状,并对认证数字水印技术的未来发展方向进行了展望。     

一种可抵抗MP3压缩的音频水印算法

提出了一种稳健的自适应混合域数字音频水印算法,该算法具有以下特点：(1)通过采纳更为稳健的同步信号及其全新嵌入策略,提高了音频水印的抗攻击能力;(2)充分利用DWT的多分辨率特性和DCT的能量压缩特性,改善了数字水印的隐藏效果;(3)结合听觉掩蔽特性自适应确定量化步长,提高了数字水印的不可感知性;(4)以保证不可感知性和稳健性的良好平衡为前提,实现了数字水印的盲检测．仿真实验表明,所提出的算法不仅具有较好的不可感知性,而且对诸如重新采样、重新量化、叠加噪声、低通滤波、随机剪切等攻击均具有较好的稳健性．特别地,该算法对于最为普通的MP3压缩攻击具有极强的抵抗能力(尤其是高压缩比下).     

A hierarchical digital watermarking method for image tamper detection and recovery

In this paper, we present an efficient and effective digital watermarking method for image tamper detection and recovery. Our method is efficient as it only uses simple operations such as parity check and comparison between average intensities. It is effective because the detection is based on a hierarchical structure so that the accuracy of tamper localization can be ensured. That is, if a tampered block is not detected in level-1 inspection, it will be detected in level-2 or level-3 inspection with a probability of nearly 1. Our method is also very storage effective, as it only requires a secret key and a public chaotic mixing algorithm to recover a tampered image. The experimental results demonstrate that the precision of tamper detection and localization is 99.6% and 100% after level-2 and level-3 inspection, respectively. The tamper recovery rate is better than 93% for a less than half tampered image. As compared with the method in Celik et al. [IEEE Trans. Image Process. 11(6) (2002) 585], our method is not only as simple and as effective in tamper detection and localization, it also provides with the capability of tamper recovery by trading off the quality of the watermarked images about 5 dB.     

Geometrically invariant color image watermarking scheme using feature points

Geometric distortion is known as one of the most difficult attacks to resist. Geometric distortion desynchronizes the location of the watermark and hence causes incorrect watermark detection. In this paper,we propose a geometrically invariant digital watermarking method for color images. In order to synchronize the location for watermark insertion and detection,we use a multi-scale Harris-Laplace detector,by which feature points of a color image can be extracted that are invariant to geometric distortions. ...     

两种抗几何攻击数字图像水印算法分析及比较

以图像归一化和不变质心理论为基础提出了两种安全性较高的数字图像水印算法。为了增加水印的隐秘性及抗干扰能力,水印在嵌入前均进行了置乱和混沌加密处理,然后两种方案分别根据其归一化图像的不变质心确定出相应的重要区域,并在该区域实施水印的嵌入。实验结果表明,提出的两种数字图像水印算法均具有较好的不可感知性和抗攻击的鲁棒性,且在抵抗常规信号处理和几何攻击下各具优势。     

图像四叉树剖分下的自适应数字水印算法

提出了一种图像四叉树矩形剖分下的自适应数字水印算法。通过对原始图像在多个尺度上进行最小二乘多项式逼近,将图像进行非均匀剖分,并以四叉树结构的形式进行表达。该四叉树结构既实现了对原始图像的逼近,同时携带了图像的纹理结构信息。通过统计各子区域上的剖分网格数目,计算不同区域上水印嵌入的强度,从而实现自适应数字水印方案。实验结果表明,该算法具有良好的透明性和顽健性。     

一种简化的基于分块模运算的安全数字水印算法

基于分块模运算的数字图像水印是一种有效的用于版权保护及盗版跟踪的空域图像水印算法。它通过在图像特征边缘点附近选择由3x3像素点所组成的块并调整该块平均亮度的值嵌入水印。然而,原算法需要存储原始图像的特征边缘点用于水印检测,而且还存在算法安全性问题。通过随机选择嵌入水印的像素块位置有效地简化了算法,并利用保持嵌入水印图像平均亮度不变改进了算法安全性。实验及理论分析证明了算法的有效性。     

医学图像数字水印的非线性方法

医学图像在存储和传输过程中,不允许做有损压缩等变换。医院给出图像必须是要负责任的,所以医学图像不允许别人改动,特别是在病灶区不能改动。为了确保达到这一目的,一种新的采用符号动力学方法的数字水印被提出。根据这一方法,在嵌入水印的时候,可以使得图像中的关键部分不需要修改。一旦有人改动图像,马上可以从水印检查中发现,可以确保图像不被别人改动。     

A novel image watermarking scheme based on amplitude attack

This paper presents a novel image watermark scheme based on the characteristics of amplitude attacks. First of all, the analysis of amplitude attacks is performed. Then the amplitude attacks are categorized into three types: positive attack, negative attack and random attack. Finally, based on these attack types, we design three corresponding detectors. The detectors remove the unreliable discrete cosine transform (DCT) coefficients in the attacked image so that only reliable coefficients are used for the extraction of the watermark embedded. The experimental results indicate that the proposed technique improves robustness significantly without sacrificing the false alarm rate.     

一种基于ICA的数字图像特征保护方法

提出一种利用数字图像的特征值对该数字图像进行保护的方法。该方法利用DCT变化原理,提取数字图像的特征值,然后采用信息论中熵的原理和独立分量分析方法评价特征值的变异程度,对数字图像进行保护。该方法不需要对原图进行修改,有较高的实用性。     

基于图像内容的非对称数字水印

在小波变换的基础上,提出了一种基于图像内容的非对称数字水印。首先,利用SOBEL算子提取经过小波分解后的低频区域中的图像的边缘特征的系数,存储在一向量中,利用非线性函数对水印加密,并将水印嵌入图像的边缘系数中。实验结果表明该算法具有极强的鲁棒性和不可见性。在实验过程中,利用MATLAB的引擎,在VC++中实现调用MATLAB的工具箱,快捷的编写了简洁的原代码。     

图像数字水印的攻击及基准测试软件

随着各种图像数字水印算法的提出，对所有数字水印方案引入一个合理、统一的基准测试软件将对数字水印的发展起到很好的促进作用。文章在描述影响图像数字水印系统性能参数的基础上，对数字水印的各种典型的攻击方式作了较完整的分析，最后对现有的基准测试程序Stirmark进行了探讨，指出了其需改进之处。     

基于结构化编码的抗剪切图像数字水印

提出了一种利用辅助信息的抗剪切数字水印算法。该算法通过对数字水印进行结构化编码使其具有标识功能,并设计了相应的结构化嵌入和提取策略。实验结果表明,算法提取效果好,速度快,能够有效地抵抗剪切攻击和一些常规攻击。     

基于线性同余的数字图像置乱与数字水印技术

为了实现数字图像的安全保密,提出了一种数字置乱加密技术和数字水印植入技术.探讨一类特殊的图像矩阵变换--Lebmer提出的线性同余模型,将线性同余模型扩展为数字图像的位置置乱加密算法,根据线性同余的规则提出了一种新颖的数字水印植入技术.实验结果表明,该算法可以在一定程度上满足数字图像加密和隐藏的鲁棒性要求.     

Adaptive reversible image watermarking scheme

This paper presents an adaptive block sized reversible image watermarking scheme. A reversible watermarking approach recovers the original image from a watermarked image after extracting the embedded watermarks. Without loss of generality, the proposed scheme segments an image of size 2^N × 2^N adaptively to blocks of size 2^L × 2^L, where L starts from a user-defined number to 1, according to their block structures. If possible, the differences between central ordered pixel and other pixels in each block are enlarged to embed watermarks. The embedded quantity is determined by the largest difference in a block and watermarks are embedded into LSB bits of above differences. Experimental results show that the proposed adaptive block size scheme has higher capacity than conventional fixed block sized method.