基于Harris特征点和伪Zernike矩的鲁棒水印算法

抵抗几何攻击的鲁棒性是目前数字水印技术中的热点亦是难点。文中以Harris检测算子和伪Zernike矩为理论基础,提出一种有效抵抗几何攻击的鲁棒水印算法。通过提取归一化图像的Harris特征点,选取部分稳定特征点确定圆形区域并计算伪Zernike矩,并量化调制伪Zernike矩的幅值来嵌入水印信息。实验结果表明,本算法对于抗几何攻击具有较好的鲁棒性,同时也能抵抗常规的信号处理攻击。     

基于图像尺度空间的几何不变特征点提取算法

图像特征点的提取是实现抗几何攻击数字水印算法的重要步骤，所提取的特征点是否鲁棒，将直接影响抗几何攻击水印的鲁棒性．Harris—Laplace角点检测方法是一种多尺度抗几何攻击角点提取方法，但计算比较复杂．将Harris．Laplace角点检测方法进行改进，把直接分析图像局部灰度值的角点提取方法与图象尺度空间的思想相结合，并兼顾多尺度的不同权值，则既可以保证角点抵抗一般几何攻击的鲁棒性，又减少计算复杂度的，根据此思路提出了加权平均Harris-Laplace角点检测方法来提取特征点．实验结果表明，该算法提取的图像特征点不仅具有很好的抵抗图像裁剪、几何缩放能力，而且计算复杂度明显低于相同重复检测率的Harris—Laplace角点检测算法．     

一种基于特征点模长的三维网格数字水印算法

提出一种基于特征点模长的三维网格模型数字水印算法。该算法根据各个顶点的邻接三角面的法线方向提取用于嵌入水印的特征点;比较特征点的模长和其所有邻接点的平均模长;根据所嵌入的水印来修改特征点模长。实验结果表明,该算法水印具有良好的不可见性,对几何变换攻击、噪声攻击等具有良好的鲁棒性。     

基于特征点和BCH码的大容量水印嵌入方案

针对目前大部分水印算法嵌入容量小、抗剪切等几何攻击性能差的缺点,提出一种利用特征点对匹配关系进行图像矫正,并通过BCH码进行纠错的大容量水印嵌入方案。本方案利用SURF算法从原始图像和受攻击图像中分别提取特征点,结合向量匹配法及RANSAC算法进行误匹配特征点对排除,根据特征点对间的坐标关系,用最小二乘法拟合出仿射矩阵进行图像矫正。实验结果表明,本算法具有水印嵌入容量大、鲁棒性强、透明性好等特点。     

基于纹理特征的鲁棒图像水印算法研究

文章提出了一种新的基于图像纹理特征分块的鲁棒水印算法.算法提取载体图像抗攻击性较强的特征向量,对其进行分级聚类分析,从而自适应地确定水印嵌入的最佳区域.为了在保证水印不可见感知的前提下最大限度地提高水印的嵌入能量,本文给出了采用加法嵌入公式时水印最大嵌入强度估计.实验结果表明,该算法在保证图像质量的前提下,对几何同步、噪声干扰、剪切、JPEG压缩等攻击具有较强的鲁棒性.     

一种基于特征的自适应水印算法

基于图像多尺度空间理论和扩频机制以及视觉感知模型的特性,给出一种基于特征的数字图像水印算法。算法采用尺度不变特征变换算子提取图像的局部不变特征区域,根据信噪比特点自适应选取水印嵌入强度因子,将一幅二值水印图像嵌入到原始图像中,实现了数字水印的不可感知性和鲁棒性。仿真结果表明,该算法对添加噪声、压缩、旋转等常见的图像处理攻击具有较强的鲁棒性。     

基于重同步的高容量鲁棒图像水印算法

如何有效地抵抗组合几何攻击,并且提高水印的嵌入容量,一直是数字水印领域一个具有挑战性的课题.针对此种状况,本文提出了一种抗组合几何攻击,且嵌入容量较大的水印算法.首先利用SURF算法从受攻击的图像提取特征点,并与原图像中的少量鲁棒性较强的特征点匹配,根据特征点对间的坐标关系准确估计出仿射矩阵;然后根据仿射矩阵对失真的图像进行几何校正,恢复水印的重同步.由于几何攻击与还原过程中的像素插值仍会导致变换域水印的位置发生细微的误差,本文在空间域嵌入一层定位水印以便精准地同步;最后,考虑到LT码具有良好的纠删性能,因而先将变换域水印信息进行LT码编码,以尽量提高算法的抗剪切性能.实验结果表明,该算法不仅实现了较高容量的嵌入,而且对于剪切、组合几何攻击具有较好的鲁棒性.     

基于局部Tchebichef矩的鲁棒图像水印算法

针对目前基于图像不变特征水印算法不能同时有效抵抗常规图像处理和几何攻击这一问题,提出了一种基于局部Tchebichef矩(LTMs)的图像水印新算法。首先,利用Harris-Laplace检测算子提取载体图像多尺度空间中的特征点,并通过特征选择策略获得稳定且分离的局部圆形特征区域;然后,结合主方向对齐,得到具有旋转、缩放和平移(RST)不变性的局部圆形特征区域;最后,计算局部特征区域的Tchebichef矩,采用量化调制Tchebichef低阶矩幅值将水印嵌入到局部特征区域中。实验结果表明,本文算法在获得很好的不可见性的同时,对常规图像处理、几何攻击及组合攻击具有较好的鲁棒性。     

一种基于图像特征点的数字水印嵌入方法

如何有效抵抗去同步攻击是数字图像水印研究领域的热点问题之一.本文提出了一种可有效抵抗去同步攻击的图像水印新算法.该算法首先利用Harris-Laplace算子从载体图像中提取尺度空间特征点;再结合特征尺度自适应确定局部特征区域;最后,采纳DFT中频幅值量化策略将水印重复嵌入到多个不相交的局部特征区域中.检测时,利用特征点实现水印的重同步,无须求助于原始图像.仿真结果表明,本文算法不仅具有较好的透明性,而且对常规信号处理和去同步攻击均具有较好的鲁棒性.     

Blob-Harris特征区域结合CT-SVD的鲁棒图像水印算法

为了提高水印图像对几何攻击的鲁棒性,提出了一种Blob-Harris特征区域结合轮廓波变换(Contourlet transform, CT)和奇异值分解(singular value decomposition, SVD)的鲁棒图像水印算法。首先在原始图像经过Contourlet变换后的低频分量中提取斑点(Blob)块区域并利用Harris角点检测进行特征点提取,然后根据各个特征点的特征尺度确定其特征区域,选择适中的互不重叠的特征区域,将其四周补零后进行归一化操作,最后将经过小波变换提取的低频水印图像进行奇异值分解,并重复嵌入到每一个归一化圆形特征区域的内接正四边形当中。仿真实验结果表明,本文算法除了对常规攻击有很好的抵抗力之外,对几何攻击也有相对较强的鲁棒性,特别是缩放、平移、剪切以及其组合攻击,NC值均达到0.94以上。      

A Novel DIBR 3D Image Watermarking Algorithm Resist to Geometrical Attacks

A histogram shape based method is utilized to design watermarking algorithm to protect the Depthimage- based rendering (DIBR) 3D images. To make the watermarking method robust to common attacks, much more suitable pixel groups are selected for watermark embedding which are insensitive to geometric attacks. Taking into account the adjusting of baseline distance in DIBR process might affect the watermarking extraction, a postprocessing is proposed after DIBR process to make the proposed watermarking method much more robust to DIBR process. As the experimental results shown, the proposed method is much more robust to the geometric attacks and combined attacks compared with existing methods. In addition, the proposed watermarking method also has good robustness to the adjusting of baseline distance and depth image blurred.     

抵抗仿射变换攻击的多比特图像水印

目前,大多数鲁棒图像水印所面临的最大问题就是几何攻击,而几何攻击又以仿射变换为主,攻击者只需对目标图像做轻微的几何形变就可以使嵌入其中的水印信息失效。本文在Ping Dong等人提出的基于图像归一化方法的抵抗任意仿射交换攻击的鲁棒数字水印的基础上,改进了原有的归一化方法,去掉了归一化过程中的约束条件,简化了归一化的过程。并且在此基础上提出一种新的水印嵌入方案,克服了文献[1]中水印方案水印不可见性较差的问题。实验证明,本文提出的方案对仿射变换攻击具有很好的鲁棒性,嵌入的水印容量较大且水印图像的质量较高。     

Geometrically invariant image watermarking based on fast Radial Harmonic Fourier Moments

In order to reduce the time complexity and improve the reconstruction performance of traditional method for Radial Harmonic Fourier Moments (RHFMs), we introduce a fast and precise method by using FFT and based on the which, this paper proposes a novel image watermarking algorithm which is robust to geometric attacks. We firstly compute the RHFMs of the original image by using the proposed method and select the robust RHFMs which are suitable for watermark embedding. Then the watermark is embedded by modifying the magnitudes of RHFMs based on quantization. In the decoder, the watermark can be extracted from the magnitudes of RHFMs directly without using the original image. Simulation results show the proposed algorithm provides an excellent watermark invisibility and can be resilient to geometric attacks and common image processing attacks effectively.     

An Oblivious Watermarking for 3-D Polygonal Meshes Using Distribution of Vertex Norms

Although it has been known that oblivious (or blind) watermarking schemes are less robust than nonoblivious ones, they are more useful for various applications where a host signal is not available in the watermark detection procedure. From a viewpoint of oblivious watermarking for a three-dimensional (3-D) polygonal mesh model, distortionless attacks, such as similarity transforms and vertex reordering, might be more serious than distortion attacks including adding noise, smoothing, simplification, remeshing, clipping, and so on. Clearly, it is required to develop an oblivious watermarking that is robust against distortionless as well as distortion attacks. In this paper, we propose two oblivious watermarking methods for 3-D polygonal mesh models, which modify the distribution of vertex norms according to the watermark bit to be embedded. One method is to shift the mean value of the distribution and another is to change its variance. Histogram mapping functions are introduced to modify the distribution. These mapping functions are devised to reduce the visibility of watermark as much as possible. Since the statistical features of vertex norms are invariant to the distortionless attacks, the proposed methods are robust against such attacks. In addition, our methods employ an oblivious watermark detection scheme, which can extract the watermark without referring to the cover mesh model. Through simulations, we demonstrate that the proposed approaches are remarkably robust against distortionless attacks. In addition, they are fairly robust against various distortion attacks     

Study on semantic-based video watermarking method

A new video watermarking method for the Audio Video coding Standard (AVS) is proposed. According to human visual masking properties, this method determines the region of interest for watermark embedding by analyzing video semantics, and generates dynamic robust watermark according to video motion semantics, and embeds watermarks in the Intermediate Frequency (IF) Discrete Cosine Transform (DCT) coefficients of the luminance sub-block prediction residual in the region of interest. This method controls watermark embedding strength adaptively by video textures semantics. Experiments show that this method is robust not only to various conventional attacks, but also to re-frame, frame cropping, frame deletion and other video-specific attacks.     

A Robust, Digital-Audio Watermarking Method

Most of the previous audio-watermarking schemes are robust to common signal-processing attacks, but show severe problems when faced with desynchronization attacks. To solve the problems associated with these approaches, we propose an audio-watermarking scheme based on support-vector-machine (SVM) theory to protect against desynchronization attacks by using audio statistics characteristics and a synchronization code technique. Experimental results with SVM show that our proposed scheme is inaudible, robust against common signal processing, and robust against desynchronization attacks.     

Robust semi-blind video watermarking based on frame-patch matching

In this paper, we present a frame-patch matching based robust semi-blind video watermarking using KAZE feature. The KAZE feature is employed for matching the feature points of frame-patch with those of all frames in video for detecting the embedding and extracting regions. In our method, the watermark information is embedded in Discrete Cosine Transform (DCT) domain of randomly generated blocks in the matched region. In the extraction process, we synchronize the embedded region from the distorted video by using KAZE feature matching. Based on the matched KAZE feature points, RST (rotation, scaling, translation) parameters are estimated and the watermark information can be successfully extracted. Experimental results show that our proposed method is robust against geometrical attacks, video processing attacks, temporal attacks, and so on.     

基于几何矩的抵抗RST攻击的数字图像水印

目前大多数的数字图像水印方案不能有效抵抗几何形变的攻击,这一弱点已成为数字水印技术走上商用的瓶颈。在各种几何形变中,RST(旋转、缩放、平移)是最为常见的攻击方式。该文提出了一种具有普适性的能够抵抗RST攻击的多比特数字图像水印方案,采用的主要措施有:(1)提出一种基于几何矩的图像标准化方案以抵抗几何攻击;(2)采用扩谱方法构造二维CDMA水印信号,实现多比特水印嵌入;(3)根据HVS特性自适应调整水印的嵌入强度,在鲁棒性和不可见性之间达到平衡;(4)利用MAP和相关方法估计和检测水印信号。实验表明该方案对RST具有很高的鲁棒性,对压缩、滤波等常见的图像处理攻击同样具有良好的鲁棒性。     

Denial of service detection using dynamic time warping

With the rapid growth of security threats in computer networks, the need for developing efficient security-warning systems is substantially increasing. Distributed denial-of-service (DDoS) and DoS attacks are still among the most effective and dreadful attacks that require robust detection. In this work, we propose a new method to detect TCP DoS/DDoS attacks. Since analyzing network traffic is a promising approach, our proposed method utilizes network traffic by decomposing the TCP traffic into control and data planes and exploiting the dynamic time warping (DTW) algorithm for aligning these two planes with respect to the minimum Euclidean distance. By demonstrating that the distance between the control and data planes is considerably small for benign traffic, we exploit this characteristic for detecting attacks as outliers. An adaptive thresholding scheme is implemented by adjusting the value of the threshold in accordance with the local statistics of the median absolute deviation (MAD) of the distances between the two planes. We demonstrate the efficacy of the proposed method for detecting DoS/DDoS attacks by analyzing traffic data obtained from publicly available datasets.     

Improved robust VQ-based watermarking

A robust watermarking method based on vector quantisation (VQ) is proposed as an improvement to existing VQ watermarking techniques. Experimental results illustrate that the proposed method exhibits superior performance compared to existing techniques for a variety of attacks.