A majority-voting based watermarking scheme for color image tamper detection and recovery

This paper presents a novel color image watermarking scheme for both tamper detection and tampered image recovery. The proposed scheme embeds watermarks consisting of the authentication data and the recovery data into image blocks. In the tamper detection process, instead of independently examining each embedded authentication data, we take all the authentication data embedded in an image into account and utilize a majority-voting technique to determine the legitimacy of image blocks. Experimental results show that the proposed scheme can effectively thwart collage attack and vector quantization (VQ) attack, while sustaining superior accuracy of tamper localization. Furthermore, the results reveal that the tampered images can be successfully recovered with acceptable visual quality.     

基于混沌的图像自恢复安全双水印算法

为提高图像自恢复双水印算法的安全性,提出一种基于混沌的安全双水印算法。该算法首先利用混沌映射将双水印信息加密后再嵌入其他图像块的低位,然后结合图像块内容和嵌入在图像块低位的恢复水印信息,利用混沌映射随机生成用于检测图像块真实性的认证数据。理论分析和实验结果表明该算法在保持篡改恢复质量和不可见性的基础上,有效提高了自恢复双水印算法抵抗内容篡改攻击和字典搜索攻击的能力。     

Stereo image watermarking scheme for authentication with self-recovery capability using inter-view reference sharing

Advances in three dimensional video is a strong stimulus for research in authentication of stereo image to avoid illegal modification. In this paper, a stereo image watermarking scheme is proposed for authentication with self-recovery capability using inter-view reference sharing. A mechanism of inter-view reference sharing in stereo image pairs is designed to reduce bits for recovery reference generation compared with independent references. Discrete wavelet transform coefficients are employed to generate the references, and two reference copies of each block embedded in two different mapping blocks are prepared for recover tamper. Moreover, detail information from high frequency coefficients is also embedded so as to improve the quality of tamper recovery. For the purpose of resisting collage attack and increasing the probability of tamper detection, disparities between pairs of matched blocks are checked to conduct tamper detection. Experimental results show that the proposed scheme can detect tampered blocks with the probabilities of more than 99 % after collage attack. When stereo images are cropped from 10 to 70 % with randomly tampering, they are recovered without losing main visual information and qualities of recovery are better than those of existing monocular image watermarking schemes extended to stereo images.     

Novel image authentication scheme with fine image quality for BTC-based compressed images

A novel image authentication scheme which can protect the image integrity of the compressed images for block truncation coding (BTC) is proposed in this paper. In the proposed scheme, the authentication codes are embedded into the the quatization levels of each BTC-compressed image block by using reference matrix– RM_B. The size of the authentication codes can be decided according to the user’s requirement by adjusting the value of B in Reference Matrix. The experimental results demonstrate that the proposed method outperforms previous approaches in image quality of the embedded image and high detecting accuracy.     

Probability-based reversible image authentication scheme for image demosaicking

In this paper, we propose a novel image authentication scheme to detect the tampered areas for image demosaicking with the reversibility preserving property. Image demosaicking is the process of reconstructing an RGB color image from the sampled data acquired by the digital camera that applies a color filter array to a single sensor. In the proposed scheme, the authentication data is embedded into the rebuilt components of the demosaicked pixels.From the results, it is shown that good image qualities of the embedded images are obtained by using the proposed scheme. When the illegal users modified the contents of the embedded images, the tampered areas in the modified images can be clearly detected by using the proposed scheme. The demosaicked images can be losslessly recovered if no modifications are done on the embedded images. The proposed authentication codes embedding process can be implemented by hardware in single sensor digital camera. Furthermore, the proposed scheme can be extended to protect the image integrity for cloud computing environments.     

抗JPEG压缩并精确定位篡改自嵌入水印算法

为了提高自嵌入水印算法篡改定位的精确度和抗JPEG压缩性能,提出了一种用于图像篡改定位和恢复的双水印算法。该算法对图像进行一级小波分解,分别在高频和低频分量中嵌入认证水印和自恢复水印。仿真实验表明,该算法不仅能对篡改区域实现精确定位,而且具有较好的鲁棒性,可以抵抗一定的JPEG压缩。     

一种篡改检测与篡改定位分离的图像认证方案

针对脆弱水印认证算法的篡改定位精度及安全性问题,提出了一种将篡改检测和定位分离的图像认证方案:对图像进行单像素置乱并将其低两位置零,采用像素关联技术生成各个像素的篡改定位水印,并将其嵌入到自身的次低位;将图像逆置乱后并进行分块,生成各个分块的篡改检测水印,将篡改检测水印嵌入到各像素的最低位,进而生成含水印图像.理论分析和实验结果表明:该方案可以抵抗目前针对单像素认证算法的Oracle攻击及针对分块算法的量化攻击,在保证系统安全性的同时可将篡改定位到单个像素.     

A new data hiding scheme for binary image authentication with small image distortion

A new data hiding scheme for binary image authentication that has a small distortion of the cover image is proposed in this paper. Using the data-embedding algorithm that is based on Hamming codes, the proposed scheme embeds authentication information into the cover image with flipping only a small number of pixels. A special type of the pixels are selected and flipped by a new algorithm to minimize visual distortion. This new algorithm is based on ELSSM (Edge Line Segment Similarity Measure). Randomly shuffling the bit-order of the authentication information to be embedded, the information can only be extracted by the designated receiver who has the symmetric key. We employ two measurement metrics: miss detection rates for the degree of security and PSNR (Peak Signal-to-Noise Ratio) and ELSSM for the degree of the image distortion to demonstrate the feasibility of the proposed scheme. Using these metrics, we analyze the proposed scheme and the previous schemes. The analysis reveals that the proposed scheme requires less image distortion than the previous schemes whilst achieving the same level of the miss detection rate. Experimental results demonstrate that the proposed scheme is more resilient against recent steganalysis attacks than the previous schemes.     

An efficient fragile watermarking scheme with multilevel tamper detection and recovery based on dynamic domain selection

Self-recoverable fragile watermarking is meant for accurate tamper localization as well as image recovery with superior visual quality. However, most of the existing state of art approaches perform authentication and recovery on block basis owing to which the entire block is categorized as tampered in case of alteration of one or more pixels of it. This, results in staircase formation of tamper detected regions, hence lacking in accuracy. Furthermore, the visual quality of the recovered image also deteriorates as an approximate value is assigned to all the block pixels corresponding to the altered region. The proposed watermarking scheme performs both authentication and recovery pixelwise. The authentication of each pixel is done via multi level tamper detection(MLTD) through three authentication bits based on value, location and neighbourhood information. The domain for image recovery is chosen dynamically based on the content of the block, may it be in spatial domain for smooth blocks or frequency domain for the rough ones. This provides high accuracy in recovery. As the embedding of recovery information is done in the frequency domain, the imperceptibility of the watermarked image scheme remains high. Also, embedding of authentication information in the spatial domain maintains its fragile nature. Even for higher tampering ratios, the lost content is rebuilt with high peak signal to noise ratio(PSNR) of the recovered image. The probabilities of false rejection and false acceptance head towards the ideal value for most of the empirical analysis. Comparative study via metric evaluation of probability of false rejection (PFR), probability of false acceptance (PFA) and PSNR of recovered image for different standard test cover images demonstrate the efficacy of the proposed scheme over other existing state of art approaches. Further, the security of the proposed scheme remains high due to usage of multi-layered secret keys and chaos based random mapping handling worst tamper scenarios.     

窜改认证与内容恢复分离的自嵌入脆弱水印算法

为了提高可恢复水印的认证精度和恢复质量,降低虚警率,提出了一种窜改认证与内容恢复分离的自嵌入水印算法。该算法以2×2的图像块为认证单位,将认证水印与恢复水印分别嵌入到自身图像块和偏移图像块中,使认证虚警率降为0;同时提出一种基于线性函数和混沌映射的偏移值选取方案,使图像的恢复质量得到提高。理论分析和实验结果表明,该算法能在抵抗拼贴和量化攻击的同时,准确定位图像窜改并以较高的质量进行恢复。     

Medical image authentication using SLT and IWT schemes

Over the years, different watermarking techniques have been used for medical image authentication purposes. Some techniques have been presented to detect tampering in the medical image while others can also recover the tampered region after the tamper detection. Many of the previous medical image authentication schemes have successfully achieved their aims; however, the robustness of the authentication scheme against unintentional attacks has not been highlighted sufficiently. This paper presents a new medical image authentication scheme in which the medical image is divided into two regions (i.e., region of interest (ROI) and region of non-interest (RONI)). Then two watermarking methods based on Slantlet transform (SLT) are used to embed data in the ROI and the RONI. The proposed scheme can be used for tamper detection, localization, and recovery in addition to the data hiding. To generate the recovery information of the ROI, a new method has been proposed based on the integer wavelet transform (IWT) coefficients. The experiments that have been conducted to evaluate the proposed authentication scheme proved that it is efficient not only in achieving its main tasks that have been mentioned above but also in having robustness against unintentional attacks (i.e., JPEG compression, additive Gaussian noise (AGN), and salt-and-pepper noise) and that makes it more suitable for the practical applications.     

一种基于分块DCT的混沌半脆弱图像水印技术*

提出了一种用于数字图像内容认证的半脆弱水印方案。将图像进行分块,图像块的归一化标准差经量化操作后映射为混沌系统初值,经混沌映射生成水印比特。用量化系数技术将水印比特嵌入块DCT直流系数。利用混沌对初值极端敏感性的特点,能够定位检测对加入水印图像的窜改,并且水印提取不需要原始图像。实验结果表明,嵌入水印后图像的视觉质量好;算法具有对图像内容局部窜改检测的有效性、敏感性以及良好的窜改定位能力,并具有更好的抗JPEG压缩、加性高斯噪声和中值滤波的鲁棒性。     

应用整数提升小波的图像变容量恢复水印方案

传统的可恢复水印算法往往是通过增加嵌入水印容量来提高篡改图像恢复质量,这将导致嵌入水印后图像质量的下降。针对这一问题,提出使用整数提升小波构建变容量恢复水印算法。该算法根据2×2图像块的纹理特征,使用小波系数生成长度可变的恢复水印,加密后嵌入其他映射图像块低位。使用恢复水印,结合相邻块特征进行篡改图像的检测与恢复。实验结果表明新算法能很好地满足水印不可见性要求,能有效抵抗剪切、拼贴及涂鸦等攻击,能更好地实现篡改图像的恢复。     

一种基于DCT变换的图像认证算法

提出了一种可自恢复的图像篡改认证算法,原始图像的最低位和3／4次低位置零和进行2×2分块DCT变换的基础上,提取DC分量组成图像矩阵,DC分量量化产生特征图像。特征图像经过Arnold置乱,将其二值编码作为水印并混沌加密后嵌入到原始图像的最低位和3／4次低位。实验结果表明,该算法简单、安全性高,篡改精确定位到2×2图像块,可对篡改区域近似恢复,具有较好的实用性。     

抗拼贴攻击的二值图像认证算法

为提高算法抵抗拼贴攻击的能力,本文结合块相关思想提出一种二值图像认证算法.该算法首先将每个图像块中的像素点分为“可翻转”和“不可翻转”两类,将“不可翻转”像素点 Hash 生成水印信息,用其替代相应映射块的“可翻转”像素点实现水印嵌入.通过比较图像块重构水印及提取水印的一致性判断该图像块的真实性,并结合各图像块邻域篡改特征进一步提高篡改检测性能.实验结果表明,该算法不仅提高了在替换、添加、删除攻击下的篡改检测性能,而且能够有效抵抗拼贴攻击.     

Tamper detection and self-recovery of biometric images using salient region-based authentication watermarking scheme

Biometric images can be split into regions of salient (ROI) and regions of background (ROB) based on salient region detection. During the process of watermark embedding, salient regions which contain rich-information are less affected by the watermark, therefore can be embedded into more watermarks, and regions of background (ROB) are susceptible to the effect of watermarks, so that they should be embedded lighter or even none in order to preserve the recognition quality of biometric images. In this paper, a novel scheme for tamper detection and self-recovery of biometric images using salient region-based authentication watermarking is proposed. Firstly, we propose a novel multi-level authentication watermarking scheme, which is used to verify the integrity of biometric images. Secondly, biometric data of these biometric images which is used as information watermarks is embedded into themselves. As a result, verification systems can recover the damaged data of original biometric images with hidden information based on tampering detection result. Experimental results and theoretic analysis show that our proposed scheme can detect tampered regions, and recover biometric data while keeping the recognition quality.     

A self recoverable dual watermarking scheme for copyright protection and integrity verification

Dual watermarking implies embedding of robust as well as fragile watermarks into the same cover image. It facilitates integration of copyright protection and integrity verification into the same scheme. However, most of such existing state of art approaches either lacked the feature of tamper detection and original content recovery or provided an approximation using coarser block level approach. The proposed self recoverable dual watermarking scheme integrates all the aforementioned functionalities of copyright protection, tamper detection and recovery into one scheme. The scheme is independent of the order of embedding of robust and fragile watermarks as these are embedded in different regions of the cover image. It performs tamper detection and recovery, both at the pixel level. The scheme obtains recovery information for each 2×2 image block in just eight bits which are further encoded to only four bits via mapping table. This reduction in recovery bits allows efficient embedding of copyright information which is tested against comprehensive set of attacks. The scheme is found to be robust against noises, filtering, histogram equalization, rotation, jpeg compression, motion blur etc. Besides the normalized cross correlation value, the evaluation of the extracted copyright information is also being done using various objective error metrics based on mutual relation between pixels, their values and locations respectively. The imperceptibility and visual quality of the watermarked as well as recovered image is found to be satisfactorily high. Three major categories of images: natural, texture as well as satellite have been tested in the proposed scheme. Even minute alterations can be chalked out as the detection accuracy rate has been enumerated on pixel basis. The scheme can tolerate tampering ratios upto 50 percent though the visual quality of the recovered image deteriorates with increasing tampering ratio. Comparative results based on normalized cross correlation, probability of false acceptance, probability of false rejection and peak signal to noise ratio metrics validate the efficacy of the proposed scheme over other existing state of art approaches.     

对水印信息篡改鲁棒的自嵌入水印算法

为提高自嵌入水印算法在任意篡改条件下的篡改恢复质量,提出一种对水印信息篡改鲁棒性的空域自嵌入水印算法,分析了算法中阈值选取的合理性和检测篡改的可靠性.该算法首先基于密钥将原始图像的最低位和1/4次低位置零,通过对图像内容的小波低频系数实施均匀标量量化生成低频特征图像,将低频特征图像置乱加密后生成的二值编码嵌入原始图像的置零位;认证时通过设定的阈值识别图像内容被恶意篡改的图像块,从而提高自嵌入水印算法对水印信息篡改和信道噪声的鲁棒性.理论分析和仿真结果表明,无论水印信息被随机篡改还是区域篡改,算法均能根据阈值区分不同篡改并选用不同的方法对其进行篡改恢复,有效地提高了自嵌入算法在部分水印信息篡改时的恢复质量.     

Hierarchical recovery for tampered images based on watermark self-embedding

In this paper, we propose a new self-embedding watermarking scheme with hierarchical recovery capability. The binary bits in the adopted MSB layers are scrambled and individually interleaved with different extension ratios according to their importance to image visual quality. The interleaved data, which are regarded as reference bits for tampering recovery, are segmented into a series of groups corresponding to the divided non-overlapping blocks, and then embedded into the LSB layers of blocks together with authentication bits of tampering detection. Because the extension ratios of MSB-layer bits are based on the hierarchical mechanism, the efficiency of reference bits is increased, and higher MSB layers of tampered regions have greater probabilities to be recovered than lower MSB layers, which can improve the visual quality recovered results, especially for larger tampering rates. Experimental results demonstrate the effectiveness and superiority of the proposed scheme compared with some of state-of-the-art schemes.     

一种基于混沌Hash函数的脆弱水印算法

针对现有分块脆弱水印的缺陷,提出了一种基于混沌Hash函数的脆弱水印算法。该方案通过将原始图像分块后做混沌Hash,生成原始图像的摘要,与由混沌映射生成的混沌二值图像异或后生成二值脆弱水印,置乱加密后嵌入原始图像的LSB平面;认证时通过差值图像定位篡改的区域。理论分析和实验仿真表明提出的水印算法不可见性好,能够有效抵抗VQ攻击,并能够区分篡改的类型,安全性高。