采用复合整数变换差值扩大法的矢量地图可逆水印算法

现有的二维矢量地图可逆水印算法没有充分考虑原始地图的形状特征,其有效信息嵌入率较低,水印嵌入带来的失真较大,为此提出一种有效的二维矢量地图可逆水印算法.该算法考虑二维矢量地图的结构特点和形状特征,利用矢量地图曲线和曲面坐标序列固有的分段单调性来构造多维向量;对多维向量实施复合差值扩大可逆变换,将水印嵌入引入的误差由多个数据点共同承担,使得每个数据点所承受的误差更均匀,避免了在矢量地图单调转折区因水印嵌入带来较大的失真,使矢量地图能承载更多的有效信息;通过设定矢量地图的误差容限来保证精度,可有效地控制信息的嵌入大小.理论分析和实验结果表明,该算法具有较好的透明性和较高的有效信息载荷,可用于矢量地图认证和隐秘通信等领域.     

矢量地图的无损数据隐藏算法研究

在矢量地图中隐含水印信息,地图数据的质量往往由于水印的嵌入而受到影响。可逆水印技术(又称无损数据隐藏)具有完整恢复载体数据的能力,因而更加适用于矢量地图。基于差值扩大的思想,提出了一种应用于矢量地图的无损数据隐藏算法。算法根据矢量地图对数据精度的特殊要求提出了相应的水印嵌入条件,并通过修改地图中相邻顶点坐标间的差值来嵌入水印信息。水印的提取过程不仅能够得到隐藏信息,而且能够准确无误地恢复原始地图数据。采用两类地图进行实验,实验结果表明,算法在具有较强坐标相关性的地图中具有较高的嵌入容量,并且引入较低的扰动。算法的应用前景包括矢量地图数据的篡改鉴别、元数据格式兼容以及基于矢量地图的隐藏通信。     

基于点模式匹配的矢量地图水印算法

提出一种基于点模式匹配的矢量地图水印算法。该算法将灰度图像嵌入到矢量地图的特征顶点中,嵌入时通过控制误差容限,保证水印的不可见性。水印的提取过程采用点模式匹配算法,通过匹配被检测的矢量地图与含水印的矢量地图的关键顶点得到它们之间的配准函数,最后与原矢量地图比较可以计算得到嵌入的水印信息图像。实验证明该算法对平移、旋转、缩放等攻击都能起到很好地抵抗,具有较高的安全性。     

一种采用曲线分割的矢量图水印算法

针对矢量图形既需具有鲁棒性又要保证图形几何精度的问题,提出了一种针对矢量图形水印嵌入、提取和检测方法。水印的嵌入算法是将一幅矢量图形视为曲线的集合,按设定阈值进行曲线分割;再在容差范围内,使每条曲线对应一个水印位,且对曲线中每个结点嵌入一个含有用户证书信息的水印点。水印提取算法则对原图和含水印图进行对应的分割;按嵌入算法的逆过程逐曲线提取出水印信息;再通过计算原水印信息和所提取水印信息的相似度检测水印存在与否和符合程度。实验结果表明,该方法在无攻击和几何变形操作攻击下的水印检测相似度均接近100;且水印图即使在剪裁了的2/3后,仍能保证大于09的相似度;同时,方法具有抗D-P压缩能力,并可借助所给出的相似度阈值经验曲线,控制水印点的偏离角度,或在水印信息检测的自动化处理流程中设定参数,起到既能保证矢量图形的精度,又具有较好的鲁棒性的作用。     

利用地理坐标网分块的矢量地图脆弱水印方案

为解决矢量地图数据的完整性认证问题,提出一种利用地理坐标网分块的脆弱水印方案.首先利用地理坐标网按照一定的经差和纬差将矢量地图划分为互不重叠的数据子块,然后对每个子块内的数据点进行排序处理,利用嵌入位前的坐标信息生成脆弱水印,最后采用防数据点溢出策略通过修改坐标嵌入位将认证信息嵌入.水印检测与嵌入过程相对应,无需借助原始数据.数据认证时,通过对比检测出水印和生成水印的一致性,判断地图数据是否遭到了篡改.采用某地1:100万的道路线状数据进行水印性能评估实验,实验结果表明,该脆弱水印方案具有良好的稳定性、不可见性和篡改定位精度,能够对矢量地图数据的完整性进行准确认证.     

基于纠错编码的矢量地图可逆水印算法*

针对当前矢量地图可逆水印算法中缺乏水印提取结果纠错方法研究的问题,提出了一种基于纠错编码的矢量地图可逆水印算法。首先采用二值数组表达版权信息并生成其纠错编码,然后将二者合并组成水印数据,最后将水印数据嵌入地图顶点极坐标以增强算法抵抗几何变换的能力。水印提取后,通过纠错编码对水印提取结果进行纠错,达到提升算法稳健性的目的。实验结果证明：该算法具有严格的可逆性、理想的隐蔽性以及较强的稳健性。     

运用混合域比值不变性的矢量地图水印算法

目的 传统基于频率域的矢量地图水印算法往往通过直接修改变换系数实现水印嵌入,嵌入位置随机,且嵌入强度难以控制,实用能力受限。为此,本文挖掘了离散小波变换（discrete wavelet transform,DWT）和复数奇异值分解（complex singular value decomposition,CSVD）系数比值作为新的水印嵌入域,融合系数放大法和量化索引调制（quantization index modulation,QIM）提出了一种嵌入强度可控的鲁棒性矢量地图水印算法。方法 利用道格拉斯—普克算法提取矢量地图特征点,并基于特征点构建复数序列,对复数序列进行二层 DWT,得到二层低频系数和二层高频系数。在此基础上,利用 CSVD 分别计算二层低频和高频系数的奇异值,并以奇异值比值作为水印嵌入域。在水印嵌入阶段,对系数比值放大合适倍数,通过调制放大后的奇异值比值来控制水印嵌入误差,并实现水印信息的盲提取。结果 与最新的 3 种方法进行比较,本文算法从平移、旋转和缩放的组合攻击中提取的水印图像的归一化相关性系数（normalized correlation,NC）值从低于 0. 6 提升至 1。此外,在裁剪、简化和几何攻击的任意组合攻击中,本文算法均能够提取出 NC 值为 1 的水印图像,相较于对比方法,鲁棒性更加全面。在不可见性方面,本文算法表现优势,水印嵌入造成的误差被控制在毫米级。结论 本文所提的矢量地图水印算法挖掘了多重频率域变换的比值作为水印嵌入域,具有良好的安全性和稳健性,可以为矢量地图的版权保护提供技术参考。     

用于矢量数字地图的可逆数据隐藏算法

提出一种基于差值直方图的可逆数据隐藏算法,用于矢量地图的认证和隐秘通信。通过修改相邻顶点坐标的差值来实现数据隐藏。为减少由扩展嵌入所引起的图形失真,借助差值直方图来选取可嵌入差值,优先选择绝对值小的差值。与现有算法相比,本算法具有较高的嵌入率、较好的图形质量以及精确控制嵌入容量的能力。     

基于网格频谱域的二维图形水印算法

提出了基于网格频谱域的二维矢量图形改进水印算法,以置乱后的二值图象作为水印,以二维矢量图形作为载体。通过修改载体图形随机挑选的网格频谱域系数来嵌入水印。水印嵌入强度能够根据图形的自身曲线弯曲变化频度特征自适应地调整。实验结果表明,相对于原算法。改进算法具有更好的安全性,且在保证水印具有较好透明性的前提下。提高了水印的健壮性。     

矢量地图水印的数据质量评价研究

含水印数据的质量评价是衡量水印嵌入隐蔽性和数据可用性的重要指标。峰值信噪比（PSNR）等基于能量的度量指标在应用于矢量地图水印系统时具有一定的局限性。从形状的角度考虑了矢量地图水印的数据质量评价问题,借鉴时间序列聚类和形状相似性匹配的思想,提出了基于距离度量的水印地图数据评价指标。算法从2维矢量地图中提取1维特征函数,通过度量水印嵌入前后特征函数的形状差异来评价含水印地图的数据质量。实验结果证明,本文提出的度量方法更符合矢量数据的特点,能够得到比现有方法更准确的度量结果。     

A key points-based blind watermarking approach for vector geo-spatial data

This paper presents a blind watermarking approach to protecting vector geo-spatial data from illegal use. By taking into account usability, invisibility, robustness, and blindness, the approach firstly determines three feature layers of the geo-spatial data and selects the key points from each layer as watermark embedding positions. Then it shuffles the watermark and embeds it in the least significant bits (LSBs) of the coordinates of the key points. A similar process for selecting the feature layers and the key points in the watermark embedding process is carried out to detect the watermark followed by obtaining the embedded watermark from the LSBs of the coordinates of the key points. Finally, the similarity degrees of three versions of the watermark from three feature layers are calculated to check if the data contains the watermark. Our experiments show that the method is rarely affected by data format change, random noise, similarity transformation of the data, and data editing.     

一种基于小波域特征树量化的数字水印算法*

首先使用尺度交互式特征检测算法提取图像小波域逼近子图的特征点,然后构造相应的特征树,最后对特征树所有节点进行量化以嵌入二值水印信息。水印信息嵌入到图像的特征之中,对JPEG,JPEG 2000以及高斯白噪音等多种处理具有较强的鲁棒性。     

一种强抗压缩的矢量地图数据盲水印算法

针对矢量地图水印强鲁棒性、数据精度和盲检测等要求,提出一种强抗压缩能力的盲水印算法。首先对地图数据进行道格拉斯-普克算法压缩,然后通过改变相邻特征点所组成的三角形的形状嵌入水印。该算法在检测水印时无需原始地图,且对平移、旋转、缩放、随机增加顶点、裁剪和压缩等攻击具有非常强的抵抗能力。实验结果表明,该水印算法具有强鲁棒性、数据精度高以及实用性的优势。     

A recursive embedding algorithm towards lossless 2D vector map watermarking

The copyright protection of two-dimensional (2D) vector map has attracted a lot of research focus due to the increasing security issues raised in recent years. One promising direction seeking the optimal tradeoff between adding watermarks and maintaining minimal distortion is the so-called lossless watermarking, i.e., after watermark extraction the 2D vector maps are fully lossless. This paper presents a novel lossless watermarking scheme for 2D vector maps based on a novel recursive embedding algorithm. In our algorithm, feature points of individual polylines are first grouped into united, upon which highly correlated unites are selected as cover data to carry out a recursive modification of its mean vertex coordinates. Such operation not only ensures lossless compression, but also enables higher payload capacity and, to a certain degree, the perception invisibility before and after the watermark extraction. We have conduced experiments on several real-world 2D vector map applications to show the effectiveness, efficiency of the proposed algorithm.     

Pseudo-zernike moments-based audio content authentication algorithm robust against feature-analysed substitution attack

Content-based audio content authentication algorithms provide a method to solve the veracity and integrity of audio content. On the basic of pseudo-Zernike moments, an audio content authentication algorithm robust against feature-analysed substitution attack is proposed, which is aimed at some insecure issues in the existing content-based audio content authentication schemes. Firstly, the audio signal is cut into non-overlapping frames and each frame is divided into two segments, and each segment is scrambled. Then, synchronization codes generated by pseudo random sequence and watermark bits generated by pseudo-Zernike moments are embedded in the first and second segment, respectively, which are completed by quantizing the modulus of pseudo-Zernike moments. The scrambled segments used to generate and extract watermark are unknown to attackers. So, it is difficult for attackers to get the watermark generated and extracted to perform feature-analysed substitution attack. The synchronization code and watermark embedding method proposed is inaudible and has excellent ability to tolerance against common signal processing operations. Compared with the existing audio watermark algorithms based on pseudo-Zernike moments, the algorithm increases the embedding capacity and improves the security of the watermarking system.     

Nonlinear scrambling-based reversible watermarking for 2D-vector maps

The reversible watermarking technique is suitable for vector maps due to its reversibility after watermark extraction. In this paper, a novel reversible watermarking scheme based on the idea of nonlinear scrambling is proposed. It begins with feature point extraction. To avoid the high-precision vector data being illegally used by unauthorized users, the algorithm nonlinearly scrambles the relative position of feature points. Then based on the proposed reversible embedding, both scrambled feature points and nonfeature points are taken as cover data, the coordinates of which are modified to embed both watermark data and feature point identification data. Finally, combined with the scrambling secret key, the original vector data can be exactly recovered with watermark extraction. Comprehensive experimental results validate that the scheme could effectively prevent the high-precision vector data from being illegally used with maintaining the basic shape of each polyline, simultaneously.     

一种基于特征点的矢量地图水印算法

提出一种基于特征点的矢量地图水印算法。在嵌入水印信息前,采用Torus自同构映射对水印图像进行置乱处理,将矢量地图分割为指定数量顶点的曲线集合,选择曲线中角度最小的顶点作为特征点,在地图精度允许的范围内,通过改变该特征点的坐标值,将制作的水印图像重复嵌入到这些特征点中。实验结果表明,该算法不仅能获得较好的地图精度,且对压缩攻击和各种裁剪攻击也具有较强的鲁棒性。     

A rubber sheeting algorithm for non-rectangular maps

Inherent errors in the conversion process (from maps to digital information) cause variations in the location of common boundary lines between adjacent maps. In order to eliminate these discrepancies and define a continuous database, the popular practice is to adjust the map’s boundaries. Preventing relative distortions between the map boundaries (which get altered) and the content of the map necessitates correcting and geometrically improving the map’s contents — a process known as “rubber sheeting”.The paper presents a new method for rubber sheeting, which is not dependent on the shape of the closed polygon circumscribing the map (to be improved), or on the number of points defining its perimeter. The method also covers the various possible relations between maps, such as adjacent maps, a map included completely within another map, a group of maps, etc.The algorithm is based on a non-rectangular bilinear interpolation over the entire area of the map. It determines systematic and random corrections, and subdivides the maps into separate influencing zones as a function of the map perimeter’s shape. The process ensures homogeneity in each map by itself, and, therefore, continuity over an entire database.     

时空特征分析结合随机密钥的压缩域数字视频水印嵌入和提取方法

针对现有水印嵌入和提取算法对滤波、压缩和噪声条件较为敏感的问题,提出了一种鲁棒的基于时空特征的压缩域数字视频水印嵌入和提取方法。提出的框架由一个公共密钥和一个私有密钥组成,用于阻止自我共谋攻击。算法对视频进行时空分析,并从压缩视频的时空特征中提取公共密钥,在本质上具有鲁棒性。首先,利用一个随机密钥从事先选取的块集合中选取候选块,进而确保水印框架的安全;然后基于压缩视频的时空特征选取出适合嵌入水印的4×4子块;最后,利用非零量化系数嵌入水印位。该水印框架允许视频位速率有限增加,并且降低了计算的开销。实验结果显示,相比其他几种对比方法,提出的方法具有较强的鲁棒性和安全性。