Greyscale image encoding and watermarking based on optical asymmetric cryptography and variational image decomposition

In this paper, a novel greyscale image encoding and a watermarking scheme based on optical asymmetric cryptography and variational image decomposition (VID) are proposed. In this proposed scheme, the greyscale watermark is encoded into a noise-like pattern by the phase-truncated Fresnel transform (PT-FrT)-based optical asymmetric cryptography. The greyscale host image is decomposed into its cartoon part and texture part by the VID technique. After that, the encoded watermark is embedded into the host image’s texture part by a discrete wavelet transform (DWT) based fusion approach. The proposed scheme can achieve a better watermark invisibility and a higher robustness by embedding the watermark into the host image’s texture part. Additionally, the proposed scheme can achieve a high security, because the PT-FrT-based optical asymmetric cryptography can resist some common cryptographic attacks. The feasibility, robustness and security of the proposed scheme have been demonstrated by extensive experiments and comparison with other relevant image encoding and watermarking schemes.     

An adaptive compressed MPEG-2 video watermarking scheme

Digital watermarking is becoming more and more important for protecting the authenticity of multimedia objects as they become easier to copy, exchange, and modify. Several watermarking schemes have been proposed in recent years, but most of them deal with still images, only some being extended over to the temporal domain for video watermarking. But again most of those approaches are applied to uncompressed video processing domain. In the subject paper, a new compressed video watermarking procedure is proposed. The developed method embeds several binary images, decomposed from a single watermark image, into different scenes of a video sequence. The spatial spread spectrum watermark is embedded directly into the compressed bit streams by modifying discrete cosine transform (DCT) coefficients. In order to embed the watermark with minimum loss in image fidelity, a visual mask based on local image characteristics is incorporated. Extensive experimental simulations demonstrate that the proposed watermarking scheme is substantially more effective and robust against spatial attacks such as scaling, rotation, frame averaging, and filtering, besides temporal attacks like frame dropping and temporal shifting.     

一种新的自适应量化数字音频水印算法

文章中提出了一种新的自适应量化数字音频水印算法，该算法首先将视觉可辨的二值水印图像降维成一维水印序列，并对水印序列进行随机置乱与BCH纠错编码，再将原始数字音频信号划分成音频数据段，最后选择音频段进行快速傅立叶变换(FFT)，并依据人类听觉系统(HAS)模型自适应确定量化步长量化FFT系数嵌入水印信息。该算法提取水印信息时不需要原始数字音频信号。仿真结果表明：该自适应量化数字音频水印算法不仅具有较好的透明性，而且对诸如叠加噪声、有损压缩、低通滤波、重新采样等攻击均具有较好的鲁棒性。     

A Robust Image Watermarking Scheme Using Z-Transform,Discrete Wavelet Transform and Bidiagonal Singular Value Decomposition

Watermarking is a widely used solution to the problems of authentication and copyright protection of digital media especially for images, videos, and audio data. Chaos is one of the emerging techniques adopted in image watermarking schemes due to its intrinsic cryptographic properties. This paper proposes a new chaotic hybrid watermarking method combining Discrete Wavelet Transform (DWT), Z-transform (ZT) and Bidiagonal Singular Value Decomposition (BSVD). The original image is decomposed into 3-level DWT, and then, ZT is applied on the HH3 and HL3 sub-bands. The watermark image is encrypted using Arnold Cat Map. BSVD for the watermark and transformed original image were computed, and the watermark was embedded by modifying singular values of the host image with the singular values of the watermark image. Robustness of the proposed scheme was examined using standard test images and assessed against common signal processing and geometric attacks. Experiments indicated that the proposed method is transparent and highly robust.     

采用量化MCLT变换系数的音频数字水印盲检算法

提出了量化 MCLT 变换系数的音频数字水印盲检新算法。嵌入的水印为视觉可辨的二值标志图像,对水印降维处理后,利用密钥通过 PN 序列发生器产生的伪随机序列调制水印信息,然后通过量化 MCLT 系数的方法将其嵌入音频中。通过大量实验,得到了决定水印鲁棒性和不可感知性的量化参数选择上限。实验结果表明,该算法对所嵌水印的音频质量未见降低,对信号处理和随机裁剪型的攻击具有很高的鲁棒性。     

基于掩蔽效应和抖动调制的盲水印方案

通过对信号处理领域抖动调制原理的分析,并结合人类视觉系统的掩蔽效应,提出了一个DCT 域盲水印模型。在MATLAB 仿真环境中,针对二值图像水印,实现了水印的预处理、嵌入、提取以及F 范数下水印检测。在水印嵌入过程中,通过自动调节量化步长改善了水印的透明性,水印检测时无需原始宿主图像,实现了盲检测,而且省略了反余弦变换过程,降低了算法复杂度。仿真实验表明,水印算法在JPEG 高强度压缩、剪切、各种噪声叠加以及多重水印等攻击下具有高鲁棒性。算法思想可应用于数字版权保护以及隐秘通讯等领域。     

改进的基于压缩感知的鲁棒性水印算法

目的 为了提高水印算法的抗攻击能力,提出一种改进的基于压缩感知的鲁棒性水印算法。方法 为了确保嵌入的水印信息在载体中分布均匀,对彩色载体图像的R, G, B分量进行N×N不重复分块后得到Rij, Gij, Bij,按照下标值不同的原则,随机选择3个颜色分块构成嵌入块;为了提高水印的鲁棒性和检测的成功率,对水印信息采用循环嵌入的方式;详细论述水印的嵌入和提取流程,并通过仿真与其他3种算法进行实验结果对比。结果 水印提取不需要原始图像的参与,具有盲检测性,水印的循环嵌入策略极大地提高了水印鲁棒性和水印检测成功率。仿真实验结果表明,重建的水印图像具有较小的失真度,算法能够很好地抵抗一系列的几何攻击。结论 算法具有较好的鲁棒性和不可感知性,实现较简单,在版权保护及信息安全领域具有一定的参考价值。     

Fragility and Robustness of Binary-Phase-Only-Filter-Based Fragile/Semifragile Digital Image Watermarking

In the fragile/semifragile digital image watermarking for image authentication, fragility or sensitivity of the embedded watermark to malicious attacks is an important problem. On the other hand, robustness to some incidental manipulations, such as JPEG compression, is required for the semifragile watermark. Recently, a binary-phase-only-fllter (BPOF)-based watermarking technique has been proposed for image authentication, where the authors embedded a watermark upon the BPOF of the Fourier spectrum of an image into the corresponding magnitude. Then, they performed image authentication by calculating the correlation between the extracted watermark and the phase information computed from the watermarked image. In this paper, we propose to use the identical ratio (IR) between the extracted watermark and the computed BPOF to detect watermark and measure the degree of authenticity. The IR is simpler, computationally efficient, and yields better watermark-detection performance when compared to the correlation-based calculation. In addition, it is found that the technique works better for fragile watermarking when compared to the semifragile watermarking. Furthermore, to accommodate semifragile watermarking, we propose to use the low-frequency ranges for watermark embedding and detection, which improves the required fragility and robustness. The performance of the improved algorithm is verified via experimental results.     

一种感兴趣区域防溢出数字水印算法

目的针对工程设计图纸、医学影像等存在大量边缘值像素点的图像在嵌入水印时容易出现像素值溢出的问题,文中提出一种基于感兴趣区域防溢出的水印方案。方法该方案使用改进后的区域生长法分割原始图像得到不规则形状的ROI,再通过填充像素值得到矩形水印嵌入区域,对该区域进行提升小波变换,并经过Arnold置乱,通过对水印嵌入区域的分块和扫描,跳过边缘像素值,使用奇偶映射的方法将制成QR码的水印信息嵌入至宿主图像。结果嵌入水印后图像边缘仍完整,像素值溢出现象得到大大改善,嵌入水印后图像峰值信噪比高于48db,水印不可见性高于一般水印嵌入方案,满足高精度图像对水印不可见度要求,且经过攻击后仍能实现水印的提取。结论该方案充分考虑到含有大面积背景和大量边缘像素值图像的特点,保证认证水印嵌入至图像关键ROI区域,在保证原图质量的基础上实现了防溢出的水印嵌入,经过攻击后提取的水印仍能够读取认证信息,在包装印刷工程中具有实际应用价值。     

DWT-based blind and robust watermarking using SPIHT algorithm with applications in tele-medicine

Malicious manipulation of digital images cannot be ignored in certain critical application like tele-medicine, where medical records of the patients (mostly in the form of diagnostic images of brain, chest, heart, lungs, etc.) need to be securely transmitted over the internet for various life-saving consultation and treatments. Watermarking is used to protect such documents from being manipulated and helps detect the authenticity of the image received. A robust and blind image watermarking technique based on discrete wavelet transform is proposed in this paper. For embedding purpose, suitable coefficients are found out using the Set Partitioning in Hierarchical Trees algorithm. Level of security is further enhanced by scrambling the watermark using Arnold transform and by making the set of embedding locations random using a secret key. Noise Visibility Function is used to compute the minimum allowable distortion for each coefficient before embedding to achieve better image fidelity. Experimental results show that the proposed scheme is robust against certain standard image processing attacks and outperforms the prior existing similar types of watermarking schemes.     

基于改良扩频技术的Contourlet域盲图像水印

提出了一种基于改良扩频技术的Contourlet盲图像水印算法。将二值水印图像经Arnold置乱后进行双极性映射,然后通过IMSS（Improved Modified Spread Spectrum）系统嵌入到宿主图像Contourlet域次高阶方向子带中能量最大的子带纹理最丰富的位置上,检测端采用相关检测并设置一最佳阈值来判决水印存在与否。实验结果表明该方案不仅具有很好的透明性,而且在常规的图像处理和攻击下比传统扩频水印有更强的鲁棒性,同时也克服了传统扩频水印在检测无水印图像时完全失败的缺点。     

一种基于YC-rC-b颜色空间和视觉特性的彩色图像水印技术

根据图像离散余弦变换频谱图特征及结合人眼对亮度和颜色的对比度敏感视觉特性,提出了一种人眼感知图像最小误差即JND阈值的计算方法,通过计算出的JND阈值,提出了一种基于YCrCb颜色空间的彩色图像水印技术方案。方案依据JND阈值筛选彩色图像的3个分量亮度图变换域频谱系数来进行水印的嵌入和提取。从水印技术方案上看,JND阈值的引入使得水印的嵌入达到最大;嵌入算法使得水印嵌入的位置具有随机性,有力地保证了水印信息的安全性。仿真实验和攻击测试表明:含水印图经压缩攻击后的图像与原始图像基本一样,提取的水印信息与原始水印基本相同;攻击后的含水印图具有较好的透明性和较高的鲁棒性。提出的基于YCrCb颜色空间和人眼视觉特性的彩色图像水印技术方案,是一种可行的、较好的彩色图像技术。     

窄色域抗打印扫描全息水印算法

目的为了提升水印抗打印扫描攻击的鲁棒性,提出一种窄色域抗打印扫描全息水印算法。方法制作打印机的ICC特性文件,应用特性文件转换宿主图像到CMYK颜色模式,从而获得适应该设备的窄色域,将制成全息图的水印嵌入到宿主图像的DWT域内。结果实验表明,该算法经历打印扫描后可顺利提取水印,且打印扫描后获得的水印图像保真度较高。与在RGB颜色模式中嵌入水印相比,该算法水印的鲁棒性和宿主图像的保真度均具有明显优势;相较于嵌入水印到默认转换的CMYK颜色模式,鲁棒性相当,该算法宿主图像的保真度具有明显优势。结论该窄色域算法可提升打印扫描过程中颜色传递的一致性,结合全息图不可撕毁的优势权衡了鲁棒性与保真度的关系,该算法有益于数字水印在防伪印刷领域的应用。     

基于Tchebichef矩的抗几何攻击图像水印

针对几何攻击容易使常规水印算法检测失败的问题,利用Tchebichef矩出色的重构性能,结合图像归一化,提出一种基于Tchebichef矩的抗几何攻击图像水印算法GWTM.该算法在水印嵌入和提取之前对图像进行几何失真的归一化,根据Tchebichef矩系数的特点,进行矩幅度修改量测试,筛选出最优矩集合.根据水印比特自适应地修改集合中的矩,并对修改后的矩进行Tchebichef重构,实现水印的嵌入.水印提取时,以最优矩集合为密钥,通过与原始图像的Tchebichef矩幅度比较提取水印.实验证明,GWTM算法能够抵抗任意角度的旋转攻击、缩放攻击及常规的信号处理攻击.     

Robust image watermarking scheme against geometric attacks using a computer-generated hologram

Robustness against geometric attacks is one of the most important issues in digital watermarking. A novel geometric robust watermarking scheme that uses computer-generated holograms as the watermark is presented. To maintain imperceptibility and robustness, a quantization embedding algorithm is adopted to embed the mark hologram into the low-frequency subband of the wavelet-transformed host image. In the detection process, the geometric distorted watermarked images are recovered first by the proposed improved geometric correction method, which is based on the scale invariant feature transform, the invariant centroid, and the pulse coupled neural network. Then the mark holograms are extracted from the recovered images. In comparison with the traditional geometric estimation method, the suggested improved geometric correction method can estimate the geometric distortion parameters more accurately and needs less auxiliary information. Compared with other watermark schemes using digital holograms, the proposed method has the distinct advantage of robustness to geometric attacks. The experimental results demonstrate that the proposed method has good robustness to resist geometric attacks and common attacks including rotation, scaling, translation, image flipping, combined attacks, filtering, occlusion, cropping, and JPEG compression.     

基于IWT-SVD和BRISK的鲁棒图像水印算法

目的 针对数字图像水印中传统奇异值分解算法存在的提取水印对角线失真和目前的特征点匹配算法速度慢引起抗组合几何攻击性能弱问题,提出基于IWT-SVD和BRISK的鲁棒图像水印算法。方法 该方案是将Logistics混沌映射置乱的水印嵌入宿主图像IWT变换后进行SVD分解的矩阵中,然后运用BRISK算法完成失真图像的几何校正,最后根据提取的水印图像特性,用邻域平均法进行对角线元素修正。结果 嵌入水印后PSNR高于42 dB,在各种常规信号处理和组合几何攻击下,NC平均值在0.95以上,提取出的水印对角线失真问题得到明显改善。结论 实验结果表明,该方案能提高图像特征点的匹配速度,性能得到增强,水印不可见性较好,进一步提升了图像的鲁棒性。     

脊波变换域盲数字水印方案

鲁棒性是数字水印最基本的要求之一,水印嵌入的位置和强度直接影响到水印的鲁棒性.本文提出了一种新的基于离散脊波变换(DRT)的盲水印算法,利用脊波变换对线状奇异性的稀疏表示特性,找出图像中视觉重要信息,并将水印嵌入其中,提高了水印的鲁棒性.根据图像局域脊波系数来选取水印嵌入强度,保证了水印的不可见性.水印提取不借助于原始图像,能实现盲提取.在强烈攻击的情况下,实验结果表明,此方法对JPEG压缩、滤波、噪声、裁剪等攻击具有很好的鲁棒性.     

Efficient digital image watermarking for mobile applications by optimising the spread spectrum technique

In this paper, the spread spectrum watermarking in wavelet domain is optimised by using a number of techniques to make it more efficient when executed by a platform running on mobile devices. The proposed techniques can be executed efficiently and consume less computational and power resources as compared to the conventional spread spectrum-based watermarking. The proposed technique represents binary bits in the watermark using symbols, wherein each symbol represents at least 2 binary bits. A symbol is then mapped into a pseudo noise sequence and embedded in the digital image. Our analytical results show that our schemes reduce the number of operations required for watermarking by ～50%, while our experimental results show that our schemes save about ～59 and ～67% in processing time and energy consumption, respectively.     

A new semi-blind watermarking algorithm using ordered Hadamard transform

An efficient and fast watermarking algorithm based on ordered Hadamard transform (HT) is proposed. Since it uses a few information of watermark image in secret key, it is categorised as a semi-blind method. In our algorithm, both host and watermark images are decomposed into non-overlapping blocks. Next, they are mapped into transform domain as Hadamard coefficients. Then, several high frequency AC components of host image are substituted with watermark coefficients without using any strength factor. Not employing this factor guarantees the embedded image to be retrieved with primary quality. Moreover, using HT offers several advantages of fastness, higher image fidelity, greater reliability of watermark detection and higher data hiding capacity. The experimental results show that our method keeps the quality of host image and is robust to common attacks. Compared to frequency domain and hybrid methods, it has advantages of shorter processing time, acceptable robustness and ease of hardware implementation.     

Optical watermark scheme based on singular value decomposition ghost imaging and particle swarm optimization algorithm

An optical image watermarking algorithm, based on singular value decomposition (SVD) ghost imaging and multiple transforms, is designed. The watermark image is first encrypted by applying an SVD ghost imaging system, then the encrypted watermark is embedded into the cover image with the help of multiple transforms, including lifting wavelet transform (LWT), discrete cosine transform (DCT), discrete fractional angular transform (DFAT) and SVD. Four sub-band images are produced from the host image by LWT and DCT. The improved DFAT, whose scaling factors and parameter are optimized by particle swarm optimization algorithm, is operated in the new matrix. Afterwards, SVD is executed in the two-part image and the encrypted watermark is embedded in the host image by mutual operation of different matrices. Simulation results validate that the proposed watermark scheme is superior in the aspects of security, robustness and imperceptibility.