基于水印的图像认证和完整性保护技术

数字水印技术的发展为解决图像认证和完整性保护问题提供了新的思路。对用于篡改检测和图像认证的水印技术做了综述。数字水印技术根据其识别差错的能力分为四种类型:易损水印、半易损水印、混合水印和自嵌入水印。最后还对水印认证技术的安全性问题进行了讨论。     

基于奇异值分解的半易损水印算法

随着数字图像在报刊杂志、医院、法庭中的广泛应用，越来越需要一种有效的图像认证方法，数字水印技术为上述问题提供了一个潜在的解决方案。本文提出了一种基于分组奇异值分解（SVD）的半易损水印技术，算法将经过伪随机排序的二值图像通过量化策略嵌入到分组SVD分解中最大的奇异值点，提取水印信号无需使用原始图像。仿真实验表明水印是不可察觉的，可将JPEG有损压缩同恶意攻击区分开来，能够准确地定位被篡改的图像内容。     

图像内容真实性认证的半易损水印方案研究

提出一种基于半易损的图像内容真实性认证方案。该算法既对不改变图像内容的一般性操作具有较好的顽健性，又能对改变图像内容的篡改操作具有较强的敏感性。在水印图像进行一般性处理后能够借助水印差别国和滑动窗检测并定位被篡改的区域。本文还从概率论的角度给出了精确的判决门限确定公式。仿真试验采用一般性操作和篡改操作相结合的方法，实验结果表明本文算法在保护数字图像内容真实性方面是可行的。     

基于图像内容的半易损水印认证算法

提出了一种用于图像完整性认证的基于内容的半易损数字水印算法。借助数字签名的思想。对原始图像进行哈希变抉，并用私钥对其加密。然后将加密后的信息作为水印信息，利用原始图像的HVS特性将水印信号嵌入到原始图像的小波域中。检测器同样对本身未作修改的部分作一次哈希变换，与原始水印信号进行比较，以此来验证图像的合法性。实验验证了该算法具有良好的鲁棒性和具有识别图像被篡改区域的能力。     

用于图像认证的小波域半易损水印算法

提出了一种新颖的用于图像认证的半易损水印算法,该算法提取图像在小波低频域的特征信息生成两个水印,一个水印主要用于篡改定位,另一个水印主要用于区分图像所经历的偶然修改和恶意篡改,从而提供了一种有效的图像选择认证机制.此外,该算法的水印生成和嵌入都在图像本身中进行,图像认证时不需要原始图像和任何有关水印的附加信息,从而提高了水印的安全性和保密性.实验结果表明,此算法能很好地将对图像内容的恶意篡改和偶然修改区分开来,并可以给出内容篡改的位置.     

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。     

抗攻击的图像水印技术综述

文章简要地探讨了抗各种攻击图像水印技术,包括一些基本概念:水印概念、水印的嵌入和提取过程、水印的分类和衡量水印的基本指标.文章把几何攻击分为图像变换攻击和剪裁攻击,图像处理攻击分为噪声攻击、滤波攻击、JPEG攻击和打印扫描拍照攻击.此外,文章探讨了图像水印抗击几何攻击和抗图像处理攻击从传统到最新的技术和方法.     

基于邻域相关算法的数字图像易损水印技术

给出了一种在空域中嵌入有意义易损水印的算法，首先根据密钥随机选取一组图像像素及其邻域，由邻域中像素的相关性选取出一个参考水印点，通过参考点和水印值来共同调整选出的图像像素值，从而完成水印信息的隐藏。检测时不需要原始图像。实验结果表明算法对有损压缩、数据替换等各种篡改操作具有很强的敏感性，通过归一化相关系数等方法可对数据的完整性作出结论。     

基于双混沌系统的抗JPEG压缩的图像认证水印算法

提出了一种新的兼具水印高安全性和高定位精度的抗JPEG压缩的图像认证水印算法.根据JPEG图像压缩过程中DCT系数的不变特性,将预先量化的DCT低频系数和水印密钥合成为混沌系统的初值.再将图像块的编号映射为混沌系统的迭代次数,经过logistic混沌迭代生成图像块水印.在水印嵌入过程中,利用另一混沌系统猫映射构造循环结构,建立图像块之间一一对应的循环关系,并将块水印嵌入到对应图像块的DCT中频系数中.实验结果表明,该算法对JPEG有损压缩具有良好的鲁棒性,同时可对图像内容的恶意篡改进行精确的检测与定位.     

图像水印抗几何攻击研究综述

稳健性是数字水印技术的一个核心问题。数字水印技术发展到今天,已有大量不同的算法,它们广泛提出了稳健性的声明。然而,绝大多数算法所强调的稳健性只不过是水印对抗一般信号处理的稳健性,它们不能抵抗甚至是微小的几何攻击。本文分析总结了当前图像水印抗几何攻击的各种方法,提出了下一步可能的发展方向,对改进和设计水印算法具有一定的指导作用。     

Improved image tamper localisation using chaotic maps and self-recovery

In this paper an image tamper localisation scheme is proposed in which authentication bits of a 2 × 2 image block are generated using the chaotic maps. Further the scheme is improved by including a self-recovery method to recover the tampered regions. To improve the quality of the recovered image, two different sets of restoration bits of a block are generated and each one is embedded into randomly selected distinct blocks. The proposed tamper detection scheme performs better than some of the recent schemes proposed by the researchers. The experimental results demonstrate the accuracy and fragility of the tamper detection scheme, and the efficacy of the recovery method.     

Watermarking based image authentication and tamper detection algorithm using vector quantization approach

In the present work, a novel image watermarking algorithm using vector quantization (VQ) approach is presented for digital image authentication. Watermarks are embedded in two successive stages for image integrity verification and authentication. In the first stage, a key based approach is used to embed robust zero level watermark using properties of indices of vector quantized image. In the second stage, semifragile watermark is embedded by using modified index key based (MIKB) method. Random keys are used to improve the integrity and security of the designed system. Further, to classify an attack quantitatively as acceptable or as a malicious attack, pixel neighbourhood clustering approach is introduced. Proposed approach is evaluated on 250 standard test images using performance measures such as peak signal to noise ratio (PSNR) and normalized hamming similarity (NHS). The experimental results shows that propose approach achieve average false positive rate 0.00024 and the average false negative rate 0.0012. Further, the average PSNR and tamper detection/localization accuracy of watermarked image is 42 dB and 99.8% respectively; while tamper localization sensitivity is very high. The proposed model is found to be robust to common content preserving attacks while fragile to content altering attacks.     

Real-time image tamper localization based on fragile watermarking and Faber-Schauder wavelet

This paper presents a real-time image tamper detection and localization based on fragile watermarking and Faber-Schauder discrete wavelet transform (FSDWT). The maximum coefficients of FSDWT are used with a logo to generate the watermark which is embedded in the least significant bit (LSB) of specified pixels of the original image. Experimental results prove the effectiveness of the proposed method through a series of attacks and affirm that the requirements of imperceptibility, fidelity, effectiveness and real-time processing are satisfied. The proposed method contains simple operations and has low complexity, hence, it is suitable for applications working on real-time.     

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.     

A self-embedding secure fragile watermarking scheme with high quality recovery

In recent years, with the development of cloud storage, more and more people upload images to the cloud for storage. However, confidentiality and integrity issues may arise during transmission and storage to the cloud. Aiming at these security problems, a fragile watermarking scheme based on the encrypted domain is proposed. A watermark is divided into two types, one is for detection, the other is for recovery. After embedding the two types of watermarks into the host image, the watermarked image will be transferred to the cloud for storage. A three-level tamper detection mechanism is used in the detection process, and the first-level tamper detection can be processed in the cloud. While in recovery process, a mechanism of “block-level detection, pixel-level recovery” is proposed to recover the tampered area. The experimental results show that the watermarked image has greatly changed the original image and guarantees the confidentiality. The three-level tamper detection mechanism can accurately detect the tampered area, the image can be effectively restored in different situations, when the tampering rate is as high as 80%, the average PSNR reaches 34.62 dB, and the average SSIM is higher than 0.93.     

数字水印技术在数字作品内容认证方面的应用

数字水印技术主要用于数字作品的版权保护、数字信息的真伪鉴别和保密通讯三大领域。电子文件的版权保护、安全性等问题越来越重要，这些需求都极大地促进了数字水印技术的发展。数字水印在帮助保持和验证数字作品的完整性上的应用具有独特的优势和广阔的前景。     

Massive-scale image retrieval based on deep visual feature representation

This paper proposes an image retrieval algorithm towards massive-scale multimedia data. In order to be consistent with human visual system, we first design a color attention function to describe the important of different image patches. Subsequently, we combine color and texture to construct candidate regions, which will be fed into a deep neural network (DNN) for deep representation extraction. Then, we design a similarity function to calculate the distance among different images, where top-ranking images are considered as the required images. Experimental results show the effectiveness and robustness of our proposed method.     

基于可分逆模糊化的脆弱水印

提出了一种时域上的水隐藏与检测算法－－基于可分逆模糊化的脆弱水印算法。其原理是将水印隐藏到图像的一行／列中，再通过高斯模糊化将水印信息进一步隐藏到其相邻的行／列中。在水印检测过程中，通过可分逆模糊化算法检测并估计出嵌入水印。实验结果表明，这种算法隐藏水印具有隐蔽性和脆弱性，同时能够对攻击方位进行准确定位，是一种很有前途的脆弱水印算法。