智能水印检测器的设计及应用

水印检测错误会严重损害水印系统的可信度.在水印实用化过程中,一个必须解决的问题是如何使水印检测器的错误率达到最小.本文提出在水印检测过程中采用智能信息处理技术-独立分量分析技术来实现智能水印检测器.利用独立分量分析的盲源分离能力,在水印检测过程中不需要任何关于原始图象、水印信号以及可能的攻击信息的情况下不仅可以检测到水印信号的存在而且可以精确的提取水印信号,提取的水印精确度取决于水印与原始图象、密钥之间的独立程度.实验过程中的攻击由Stirmark产生,实验数据证明这种智能水印检测器对Stirmark提供的各种攻击(如剪切、滤波、图象压缩、删行、删列、旋转、尺度变换以及多种攻击同时存在时都具有很好的鲁棒性,还可以进行多个水印的提取.这种新型的智能水印检测器的性能比现有的检水印测器优越很多.     

基于双通道检测的多比特盲水印最优检测器的设计

水印检测错误会严重损害水印系统的可信度。该文提出基于双谱和能量检测的双通道检测来实现最优盲水印检测器的设计,并给出了一种在小波域中的具体实现。传统检测方法检测概率会随着信噪比的下降而急剧下降。双通道检测时信噪比很小时只要有足够大的双谱信息,即可得到较高的检测概率。即使双谱信息很小时双通道检测系统退化为似然比检测系统,仍是最优的。检测器检测到指定的水印后利用独立分量分析技术进行水印盲恢复。实验过程中攻击由通用水印测试软件Stirmark产生,实验数据证明所设计的最优盲检测器对Stirmark提供的各种攻击(如剪切、JPEG压缩、删行/列、旋转、尺度变换、随机几何攻击等)具有很好的鲁棒性。实验结果说明这种最优检测器的性能优越于现有的水印检测器。     

DCT域图像水印的局部优化检测性能研究

水印检测是数字水印技术最关键的步骤之一.水印检测的传统方法是采用线性相关的方法,但是该方法存在问题.本文根据数字图像离散余弦变换(DCT)域交流系数的广义高斯分布模型,对图像水印的局部优化检测方法进行了推导,并给出了水印检测器检测性能的理论分析结果.实验结果验证了图像水印局部优化检测方法检测性能理论分析的有效性,以及实际检测性能的优越性.     

基于攻击特性互补的数字水印检测器

数字水印是网络环境下对多媒体信息进行版权保护的一项新技术，其关键在于水印检测器能否正确检测出多媒体信息中的水印信息。这里基于图像处理的攻击特性的互补提出了一种新的数字水印相关检测器。实验结果表明：此检测器可以有效地提高水印相关检测器的性能。     

数字水印相关检测的可靠性研究

目前大多数图像水印算法根据经验值确定水印相关检测时的检测门限,并且只能通过实验结果检验算法性能.本文分析了图像和水印的随机过程模型,给出了水印相关检测的统计特性,在此基础上描述了水印能量、检测门限及水印检测器误码率之间的关系,从理论上确定为保证一定的误码率而应嵌入的水印能量;对于退化的水印图像,也可根据所期望的误码率确定判决门限.因此本文对水印的相关检测的可靠性分析具有一定的普遍性.     

一种基于新的正交复数变换的鲁棒水印算法

本文提出了一种基于共轭对称列率复数哈达码变换(CS-SCHT)的鲁棒水印算法.在水印嵌入时,选择图像的CS-SCHT系数幅度作为水印载体,同时设计一种新的人眼视觉系统改善含水印图像的不可见性.检测时,运用Kolmogorov-Smirno方法估计系数幅度的近似分布.然后根据该分布构造局部最优检测器.实验表明该变换适合于水印领域,新检测器具有良好的鲁棒性,且人眼视觉系统能够改善含水印图像的视觉质量.     

水印通信模型及信息恢复

数字水印是一种将版权信息隐蔽地嵌入到原始数据中的技术，在过去的几年中得到了广泛的研究和应用。每个水印系统都包含两个主要组成部分：水印嵌入和水印提取／检测。近年来对水印的理论分析表明。数字水印与通信系统有着直接的联系。这种联系在设计高效优化的水印检测器时显得尤为重要。着重讨论在通信理论的基础上怎样设计优良的水印检测器。     

一种文本图像水印的算法研究

该文提出了一种文本图像水印的新算法。首先将文本中选定嵌入水印的区域视为一个彩色图像,对其进行离散余弦变换（DCT）,并将变换系数进行加密排序之后,则经典的乘性水印算法转变为加性算法。将排序之后的DCT系数视为分叉噪声,而水印信号为弱信号,那么利用加性噪声中弱信号榆测理论推导出一种水印检测器来检测水印信号,并对其检测性能进行了理论和实验分析。实验表明这种检测器对于高斯加性噪声、中值滤波、乘性噪音以及低通滤波等多种攻击手段都具有较好的抗攻击能力。     

一种基于相位的双倒谱数字图像水印算法

数字水印技术作为版权保护的有效手段已经成为研究的热点.结合倒谱分析法在音频水印中的成功应用,文中提出了一种倒谱域图像水印算法,将二值随机序列作为水印信号嵌入在图像的双倒谱变换系数的相位成分中,并利用相关检测器进行水印检测.实验证明,该算法具有较好的透明性,对通常的图像攻击,如噪声、中值滤波、剪切、JPEE压缩等都具有较强的鲁棒性.     

DCT域基于α稳定分布的数字图像水印检测器

提出了离散余弦变换(DCT)域基于α稳定分布的分数低阶统计量水印检测器设计的理论推导和实验证明.理论分析和实验结果表明:传统的DCT域水印检测是将变换系数的交流分量作二阶统计量Gausissian分布假设,并依此作为检测器设计依据,非二阶统计量检测范围与精度受到限制与影响;基于α稳定分布的假设更适合数字图像水印处理的实际应用,提案方法的约束条件更为宽泛,与对照方案相比,水印提取失真率降低了7.4%,且适用对象更具一般性.     

Digital watermarking robust to geometric distortions.

In this paper, we present two watermarking approaches that are robust to geometric distortions. The first approach is based on image normalization, in which both watermark embedding and extraction are carried out with respect to an image normalized to meet a set of predefined moment criteria. We propose a new normalization procedure, which is invariant to affine transform attacks. The resulting watermarking scheme is suitable for public watermarking applications, where the original image is not available for watermark extraction. The second approach is based on a watermark resynchronization scheme aimed to alleviate the effects of random bending attacks. In this scheme, a deformable mesh is used to correct the distortion caused by the attack. The watermark is then extracted from the corrected image. In contrast to the first scheme, the latter is suitable for private watermarking applications, where the original image is necessary for watermark detection. In both schemes, we employ a direct-sequence code division multiple access approach to embed a multibit watermark in the discrete cosine transform domain of the image. Numerical experiments demonstrate that the proposed watermarking schemes are robust to a wide range of geometric attacks.     

A Novel Audio Watermarking Algorithm for Copyright Protection of Digital Audio

Digital watermark technology is now drawing attention as a new method of protecting digital content from unauthorized copying. This paper presents a novel audio watermarking algorithm to protect against unauthorized copying of digital audio. The proposed watermarking scheme includes a psychoacoustic model of MPEG audio coding to ensure that the watermarking does not affect the quality of the original sound. After embedding the watermark, our scheme extracts copyright information without access to the original signal by using a whitening procedure for linear prediction filtering before correlation. Experimental results show that our watermarking scheme is robust against common signal processing attacks and it introduces no audible distortion after watermark insertion.     

基于几何矩的抵抗RST攻击的数字图像水印

目前大多数的数字图像水印方案不能有效抵抗几何形变的攻击,这一弱点已成为数字水印技术走上商用的瓶颈。在各种几何形变中,RST(旋转、缩放、平移)是最为常见的攻击方式。该文提出了一种具有普适性的能够抵抗RST攻击的多比特数字图像水印方案,采用的主要措施有:(1)提出一种基于几何矩的图像标准化方案以抵抗几何攻击;(2)采用扩谱方法构造二维CDMA水印信号,实现多比特水印嵌入;(3)根据HVS特性自适应调整水印的嵌入强度,在鲁棒性和不可见性之间达到平衡;(4)利用MAP和相关方法估计和检测水印信号。实验表明该方案对RST具有很高的鲁棒性,对压缩、滤波等常见的图像处理攻击同样具有良好的鲁棒性。     

A dual cepstrum-based watermarking scheme with self-synchronization

This study presents a supplementary cepstrum-based scheme to achieve blind audio watermarking via the mean-value manipulation. The proposed scheme can work with the conventional statistical mean manipulation to double the watermark capacity under the same framework. As these two cepstral schemes affect the spectrum in low frequencies in a superposition manner, the developed watermarking system employs the conventional scheme to initiate a start and the new one to actually embed watermark bits. During the embedding phase, the rapid variations between frames caused by the watermarking process are avoided by adding a transition space. In addition, the watermarking system maintains data synchronization through the insertion of a sinusoid-like signal which keeps synchronization with the frame rate. Experimental results confirm the robustness of the proposed scheme against various attacks, including time-scaling and time-shifting that many other watermarking techniques failed to survive through.     

Robust image watermarking based on multiband wavelets and empirical mode decomposition.

In this paper, we propose a blind image watermarking algorithm based on the multiband wavelet transformation and the empirical mode decomposition. Unlike the watermark algorithms based on the traditional two-band wavelet transform, where the watermark bits are embedded directly on the wavelet coefficients, in the proposed scheme, we embed the watermark bits in the mean trend of some middle-frequency subimages in the wavelet domain. We further select appropriate dilation factor and filters in the multiband wavelet transform to achieve better performance in terms of perceptually invisibility and the robustness of the watermark. The experimental results show that the proposed blind watermarking scheme is robust against JPEG compression, Gaussian noise, salt and pepper noise, median filtering, and ConvFilter attacks. The comparison analysis demonstrate that our scheme has better performance than the watermarking schemes reported recently.     

一种基于WLD特征的盲检测数字水印算法

提出了一种基于WLD特征的数字图像盲水印算法。在图像WLD特征的基础上通过编码、加密操作生成鲁棒安全的全局水印信息,采用扇形分块方案在图像子块DCT频域中实现水印的嵌入操作。利用WLD全局统计的特性,提取和认证水印的过程无需任何载体图像信息的辅助。实验结果表明,文中盲水印算法的不可感知性较好,同时对加性噪声、伽马校正和剪切操作等具有较好的鲁棒性,算法为认证图像信息的真实性提供了便利。     

A novel blind color image watermarking using upper Hessenberg matrix

It is a challenging work to design a blind color image watermarking scheme for protecting copyright, which is different from the existing schemes used binary image or grayscale image as watermark and is also different from other non-blind watermarking schemes. In this paper, we analyze the feature of the upper Hessenberg matrix, and propose a blind color image watermarking scheme using upper Hessenberg matrix of Hessenberg transform. Arnold transform is used to improve the security, and the MD5-based Hash pseudo-random algorithm is also used to improve the robustness. In the process of watermark embedding, the encrypted watermark information is embedded into the biggest energy element of the Hessenberg matrix by quantization technique. In the process of watermark extraction, the watermark is extracted from the attacked host image with blind manner. Simulation results show that the proposed scheme outperforms other related methods in the aspects of the invisibility, robustness, capacity and computational complexity.     

Secure watermarking scheme against watermark attacks in the encrypted domain

The homomorphic cryptosystems create a great opportunity for secure signal processing (SSP). Watermarking in the encrypted domain provides a promising solution to the security of watermarking. However, the robust performance of the watermarking scheme in the encrypted domain should be carefully considered. In this paper, we propose a robust watermarking scheme in the encrypted domain, which protects the original images from the third party embedders. The hybrid discrete wavelet transform (DWT) and discrete cosine transform (DCT) based method improves the robust performance of the encrypted domain watermarking scheme. The watermark extraction can be performed on both the plaintext and the encrypted domains. We also give an estimation of the expanding factor after watermark embedding in the encrypted domain. At last, we discuss the watermark attacks that are available in the encrypted domain. Taking Haar wavelet transform for example, we conduct the experiments on the visual quality and the robustness of our watermarking scheme, which demonstrate that the entire performance is satisfactory.     

Contourlet-based image adaptive watermarking

In the contourlet transform (CT), the Laplacian pyramid (LP) decomposes an image into a low-frequency (LF) subband and a high-frequency (HF) subband. The LF subband is created by filtering the original image with 2-D low-pass filter. However, the HF subband is created by subtracting the synthesized LF subband from the original image but not by 2-D high-pass filtering the original image. In this paper, we propose a contourlet-based image adaptive watermarking (CIAW) scheme, in which the watermark is embedded into the contourlet coefficients of the largest detail subbands of the image. The transform structure of the LP makes the embedded watermark spread out into all subbands likely in which the LF subbands are included when we reconstruct the watermarked image based on the watermarked contourlet coefficients. Since both the LF subbands and the HF subbands contain watermarking components, our watermarking scheme is expected to be robust against both the LF image processing and the HF image processing attacks. The corresponding watermarking detection algorithm is proposed to decide whether the watermark is present or not by exploiting the unique transform structure of LP. With the new proposed concept of spread watermark, the watermark is detected by computing the correlation between the spread watermark and the watermarked image in all contourlet subbands fully. The proposed CIAW scheme is particularly superior to the conventional watermarking schemes when the watermarked image is attacked by some image processing methods, which destroy the HF subbands, thanks to the watermarking components preserved in the LF subbands. Experimental results show the validity of CIAW in terms of both the watermarking invisibility and the watermarking robustness. In addition, the comparison experiments prove the high-efficiency of CIAW again.     

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.