基于HVS的小波域图像易损水印

基于小波变换,结合量化调制过程,论文提出了一种易损水印算法。该算法具有构造分层水印,便于实现水印的多分辨率嵌入;结合视觉特性量化调制,尽可能减小视觉失真;结合图像融合技术的多分辨率检测,使检测结果更准确;以技抵抗一定程度的JPEG有损压缩等特点。实验表明,嵌入的水印在易损性和鲁棒性上达到了较好的统一,能够抵抗一定程度的压缩而不影响篡改检测的精确性。     

一种能区分水印或内容篡改的脆弱水印算法

针对目前脆弱水印算法大多无法区分水印被篡改还是内容被篡改的问题,本文基于多重水印技术提出了一种能区分水印或内容篡改的脆弱水印算法.该算法由子块的主要DCT系数生成恢复水印,将其嵌入到偏移子块的次低位;待恢复水印嵌入后,将恢复水印作为子块内容的一部分生成认证水印,将其嵌入到子块的最低位.理论分析和实验结果表明:本文算法在抵抗量化攻击的同时,不仅能准确定位图像内容被篡改的位置,而且能区分是水印被篡改还是图像内容被篡改,并且在一定条件下可以对内容被篡改的区域进行恢复.     

基于自适应半脆弱水印的图像篡改检测方案

为保护数字图像版权和检测恶意篡改,实现高精度篡改定位,在充分挖掘图像特性的基础上,设计一种基于自适应半脆弱水印技术的图像篡改检测算法。算法根据感知特性将水印自适应嵌入到图像LSBs中,利用多数原则恢复水印信号,结合数学形态学滤波进行篡改检测与定位。仿真实验证实了该方案的有效性,在抵抗通常的内容保持攻击操作的同时,能实现精准篡改检测与定位。     

基于奇异值分解与安全Hash函数的图像认证方法

为了提高图像认证系统的安全性和不确定性,有效抵抗合谋攻击,提出了一种基于奇异值分解的半易碎水印算法。该算法利用基于信息-摘要算法5(MD5)的哈希函数对水印图像进行置乱加密。实验结果表明该算法对图像篡改具有较强的敏感性,对中值滤波、JPEG压缩等图像处理也有一定的抵抗能力,认证过程需要密钥才能完成,提高了安全性。     

一种新的数字音频多水印算法

本文以同时实现数字媒体的版权保护和内容认证为目标,提出一种在同一个音频文件中嵌入三个不同水印的数字音频多水印算法.鲁棒水印经置乱预处理后,通过SCS方法(Scalar Costa Scheme)嵌入音频信号的低频小波系数中,具有良好的鲁棒性.它不仅对加噪、低通滤波等常见信号处理稳健,还具有抵抗恶意替换攻击的能力,实现了音频文件的版权保护.时域SCS算法嵌入的半易损水印对一般信号操作稳健而对恶意篡改敏感并可以对篡改区域进行定位.最后通过改进的融合信息隐藏算法在时域嵌入全易损水印,它对加之于音频信号上的任何微小变化都非常敏感,可对原始文件的完整性进行认证.实验结果表明,整个系统透明性良好.三种水印提取时均不需提供原始音频信号,具有一定的实用价值.     

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.     

基于HSB与LSB的半脆弱水印算法

提出了一种能够精确定位并能恢复原图像的半脆弱数字水印算法。本算法利用LSB(最低比特位)所含水印信息大容量的特点,由于在图像篡改和水印攻击情况下HSB(最高比特位)具有相对稳定性,故利用HSB作为水印信息,利用一种新的置乱算法产生水印嵌入位置,结合混沌序列,修改该位置图像像素的LSB,完成水印的嵌入调制。实验结果表明,该算法不仅可对图像内容的恶意篡改进行精确地检测与定位,而且能够大致恢复出被篡改的原图像信息,并对原图质量的影响非常小。     

用于图像篡改定位和恢复的分层半脆弱数字水印算法

设计并实现了一种基于分层的半脆弱数字水印算法,用于图像内容完整性认证,篡改定位和恢复。在嵌入方,将水印信息嵌入到原始图像所有像素的2bit最低有效比特,其中认证水印由奇偶校验码和块与子块之间灰度平均值的比较组成;恢复水印为环面自同构映射块的平均灰度值。在检测方,采用分层思想,分3层对水印进行篡改定位和恢复。实验结果表明,该算法对局部发生的篡改可以有效地检测,精确定位并进行内容恢复,同时能够有效的抵抗矢量量化攻击。     

一种能抵抗协议攻击的脆弱水印

针对Wong提出的系列水印算法,本文给出了一种有效的协议攻击并提出了一种新的能够抵抗该协议攻击的脆弱水印算法.新算法将鲁棒性水印与脆弱性水印相结合来构造图像完整性和认证性水印.实验表明新算法不但能抵抗协议攻击,而且具有隐蔽性,能检测图像大小和像素值的改变,并能定位被改变的像素.此外,由于有了鲁棒性水印,增加了对版权的认证能力.     

一种有效的文档水印技术

针对二值纯文本图像，深入分析二值中文和英文文档图像本身结构特点，并在此基础之上结合人类视觉特性，提出了一种具有一定全局顽健性的局部易碎性数字水印方案。首先将文本图像依据内容进行分块，使每一图像子块只包含一个英文单词或一个字，然后提取该块的可嵌入水印的像素点，最后从中随机选一部分点，嵌入水印信息。实验结果表明该算法在不破坏图像质量基础上，能有效抵抗噪音等攻击，同时又能抵抗和定位对文本内容的局部篡改。     

Semi-fragile watermarking for grayscale image authentication and tamper detection based on an adjusted expanded-bit multiscale quantization-based technique

In this work, a semi-fragile watermarking scheme, for grayscale image authentication and tamper detection, is proposed. The proposed watermarking scheme is based on implementing a modified DWT quantization-based algorithm by embedding a random watermark bit sequence into the DWT domain using an expanded-bit multiscale quantization-based technique with adjusted watermarked location. Here, the watermark bit is expanded into three similar bits and embedded in a multiscale fashion into the DWT low-frequency subbands of the 2nd DWT levels (LL2, LL_HL1 and LL_LH1). An adjustment of the quantized coefficients is provided based on modifying their values to fall in more secure locations within the quantization interval. Several designed criteria were used to judge the received image by classifying it into: authenticated, incidentally or maliciously attacked with high accuracy in detecting and classifying attacks. Experimental results have shown the suitability of the proposed approach for tamper detection and accurate authentication.     

Cryptanalysis and improvement of a chaotic system based fragile watermarking scheme

In this paper, we analyze the security of a chaotic system based fragile watermarking scheme for image tamper detection proposed by Rawat et al. recently. Some errors and modification attack against Rawat et al.’s scheme are demonstrated. Both theoretical analysis and experimental results show that the fragile watermarking scheme is not security. Besides, improvement measure is presented to enhance the security of the fragile watermarking scheme.     

版权标识与篡改定位的数字图像水印方案

针对JPEG图像提出了用于版权标识和篡改定位功能的图像水印算法.水印嵌入和提取算法基于JPEG图像解压缩后的像素矩阵进行.水印算法结合了JPEG压缩核心技术DCT变换系数进行版权标识水印和篡改定位水印的嵌入和提取处理过程.水印算法性能测试对象为银行票据图像,实验结果包括给出了水印算法的图像体积增幅比、PSNR值以及水印误比特率指标结果.实验结果表明,算法在版权标识和篡改定位方面均具有较好的实用性.     

Digital watermarking for telltale tamper proofing andauthentication

In this paper, we consider the problem of digital watermarking to ensure the credibility of multimedia. We specifically address the problem of fragile digital watermarking for the tamper proofing of still images. Applications of our problem include authentication for courtroom evidence, insurance claims, and journalistic photography. We present a novel fragile watermarking approach which embeds a watermark in the discrete wavelet domain of the image by quantizing the corresponding coefficients. Tamper detection is possible in localized spatial and frequency regions. Unlike previously proposed techniques, this novel approach provides information on specific frequencies of the image that have been modified. This allows the user to make application-dependent decisions concerning whether an image, which is JPEG compressed for instance, still has credibility. Analysis is provided to evaluate the performance of the technique to varying system parameters. In addition, we compare the performance of the proposed method to existing fragile watermarking techniques to demonstrate the success and potential of the method for practical multimedia tamper proofing and authentication     

基于脆弱水印的图像认证算法研究

很多基于分块的图像认证算法为了提高安全性,采用大分块或者分块相关技术,因而牺牲了定位精度.通过对各种攻击的分析,提出了一种基于脆弱水印的图像认证方案.使用SHA512算法和基于背包问题的单向函数来产生水印,使用滑动窗口技术和层次结构来嵌入水印,使强加密算法在小分块上得以应用.该方案不但能够抵抗矢量量化等目前已知的各种攻击,而且能够将篡改定位到2×2大小的像素块上.理论分析和实验数据表明,该方案在保证系统安全性的同时,有效地提高了篡改定位的精度.     

Fragile watermarking scheme for tamper localization in images using logistic map and singular value decomposition

This paper presents a fragile watermarking scheme for tamper localization using Singular Value Decomposition (SVD) and logistic map. The proposed scheme divides the image into blocks of size 2 × 2 pixels and generates an 8-bit watermark from each block. The watermark is computed by permuting the six Most Significant Bits (MSBs) of each pixel in the block using the logistic map, followed by SVD. To secure, the watermark thus generated is further encrypted using the logistic map. This encrypted watermark is embedded into 2 Least Significant Bits (LSBs) of each pixel to enable tamper detection and localization. The experimental results demonstrate that the proposed scheme can precisely locate tampered regions under copy-paste, content removal, text addition, noise addition, vector quantization, collage, content only, and constant feature attacks. Tamper localization accuracy is better or comparable to the state-of-the-art tamper localization algorithms.     

基于混沌置乱的分块自嵌入水印算法

针对分块自嵌入水印算法的安全性和不能有效判断图像篡改块的问题,提出一种基于混沌置乱的分块自嵌入算法.该算法将由图像块生成的水印按空间位置生成二值水印图像,利用混沌序列对其置乱加密后嵌入到图像的最低位,认证时根据设定的阈值能有效定位图像内容被篡改的图像块.实验仿真和理论分析表明,该算法在保持原算法篡改恢复效果的基础上,无论是否有水印被改变,均能有效判断图像内容被篡改的图像块,且具有更高的安全性.     

Self Embedding Watermarking Using Halftoning Technique

This paper proposes a self-embedding watermarking scheme for digital images. It exploits a digital halftoning technique to transform the host image to a halftone image, in which the content features of the host image are well preserved. This halftone image is utilized as an approximate or compressed version of the host image and further adopted as a watermark. Unlike most available self-embedding watermarking techniques, in which watermark embedding, tamper detection and image recovery are block-wise-based, our scheme is a pixel-wise and block-wise composite scheme. That is, the watermark is pixel-wise permuted and embedded in the least-significant-bit plane of the host image, while in tamper detection and image recovery, a block-wise strategy is employed. This pixel-wise and block-wise complementary mechanism can overcome a common disadvantage of previous block-wise-based self-embedding watermarking techniques. Our scheme can be used for tamper detection and alteration location. Moreover, the tampered area can be approximately recovered using the extracted watermark. Experimental results demonstrate the effectiveness of the proposed scheme.