Multicarrier spread spectrum watermarking for secure error concealment in fading channel

This paper proposes a novel multicarrier spread spectrum (SS) watermarking scheme for the application of image error concealment using multicarrier-code division multiple access (MC-CDMA) with binary phase shift keying (BPSK) transmission in Rayleigh fading channel. The goal is achieved by embedding important information (image digest) which is extracted from the original image itself, and is used to introduce sufficient redundancy in the transmitted image. Half-toning technique is applied to obtain image digest from its low-resolution version. At the decoder side, data demodulation as well as watermark decoding are done using minimum mean square error combining (MMSEC) strategy. The extracted image digest is used to correct the damaged regions. The integration of SS watermarking with the existing SS modulation not only simplifies the design but also offers significant performance improvement for error concealment in fading channel. Authorized users having the knowledge of code patterns for SS watermarking can only perform the error concealment operation and the method is secured. Experimental results duly support the effectiveness of the proposed scheme.     

Improved spread spectrum: a new modulation technique for robust watermarking

This paper introduces a new watermarking modulation technique, which we call improved spread spectrum (ISS). When compared with traditional spread spectrum (SS), the signal does not act as a noise source, leading to significant gains. In some examples, performance improvements over SS are 20 dB in signal-to-noise ratio (SNR) or ten or more orders of magnitude in the error probability. The proposed method achieves roughly the same noise robustness gain as quantization index modulation (QIM) but without the amplitude scale sensitivity of QIM. Our proposed ISS is as robust in practice as traditional SS.     

结合置乱与扩频的数字水印算法

提出了一种使用置乱技术置乱水印图像，然后将Gold码用于水印结构设计的扩频数字水印算法。通过置乱技术提高了抽取数字水印的视觉效果，并可以在一定程度上弥补数字水印在嵌入、传输和抽取过程中的损耗。利用Gold码具有较多独立码的特性，以多位二进制信息为单位对置乱后的二值图像水印进行扩频调制，然后将调制信号自适应地加入到载体图像离散余弦变换域的低频分量系数中。应用Gold码使得算法可以采用较长的扩频序列，相应提高了鲁棒性。这种结合置乱和扩频的水印算法对于抵抗各种噪声、滤波和压缩等合法攻击以及其他非法攻击都具有很好的鲁棒性。     

基于扩频的数字音频水印技术研究

论述了时域、频域的扩频数字音频水印嵌入方案。通过分析相关检测的统计特性,得出伪随机序列的长度与音频载体本身的高度相关性直接影响检测的虚警和漏警概率,且通过实验仿真验证了上述结论的正确性,并归纳了目前常用的白化滤波器。讨论了扩频数字音频水印的同步问题,最后总结了当前存在的问题并对其发展进行了展望。     

一种基于DWT与DCT的图像扩频水印算法

提出了一种基于小波变换(DWT)和离散余弦变换(DCT)的图像扩频水印技术.该算法首先将原始图像进行DWT和DCT变换提取图像中重要的频率部分,将扩频后的水印图像嵌入到经变换后的原始图像中.然后利用扩频序列的自相关函数特征进行检测提取水印,将从受到攻击的图像中提取出的水印和原始水印的相似性进行计算得出实验结果,从而得出...     

A robust spread spectrum based image watermarking in ridgelet domain

A new robust method of spread spectrum based image watermarking is proposed in this article. Spread spectrum technique and scrambling are used for increasing robustness and invisibility of the algorithm. Our suggested method is carried out using ridgelet transform as an efficient transform for representing images with line singularities. In embedding part, the host image is partitioned into non-overlapping blocks and ridgelet transform is applied to each single block. In this way, a curved edge is divided into some straight edges so that ridgelet transform shows optimal performance even for complicated images with curve edges. To embed the watermark bits, the best directions of ridgelet coefficients are selected with respect to their variance intensity. In extraction part, a computationally efficient detection method is used for detecting watermark logo blindly from distorted watermarked image. To achieve more robust algorithm firstly, we find the best place to insert the watermark bits and secondly, we encode the scrambled watermark bits by pseudo random sequences with an authentication key. Robustness of our proposed method is tested against different kinds of attacks. According to the experimental results, proposed method shows much improved performance in comparison to other published works.     

多媒体数字水印技术

本文介绍了一种新型数字产品保护技术－数字水印,它利用数据隐藏技术将特定的信息嵌入到数字产品中,达到保护数字产品版权和数据完整性的目的。本文介绍了数字水印技术的特点和发展两头具体分析了几种方案和实际应用情况。     

扩频水印鲁棒性分析

数字水印的鲁棒性是水印技术实用化的一个重要指标。与通过StirMark测试和各种仿真测试不同,本文定义互信息作为代价函数,建立扩频水印系统鲁棒性描述和度量的一般模型,并对加性扩频水印的鲁棒性进行详细分析,推导出评估鲁棒性的互信息度量计算模型,仿真分析了盲检测和非盲检测条件下互信息函数对鲁棒性的评估结果。实验以统计误比特率的方法计算图像DCT域中低频系数为载体的扩频水印误码率,当水印噪声比变化时,互信息函数和误码率之间的匹配关系验证了互信息度量模型的有效性。互信息函数可以作为代价函数评估水印的鲁棒性,并预测误码率的变化趋势。      

Secure reversible visible image watermarking with authentication

This paper proposes a secure reversible visible watermarking approach. The proposed pixel mapping function superposes a binary watermark image on a host image to create an intermediate visible watermarked image. Meanwhile, an almost inverse function generates the recovery data for restoring the original pixels. To prevent unauthorized users from approximating the original pixels in the watermarked region, this method adds an integer sequence in the intermediate watermarked image. The sequence is composed of integers generated by two random variables having normal distributions with zero means and distinct variances. The variances facilitate a trade-off between the watermark transparency and the noise generated by unauthorized users. The proposed method also uses Lagrange multipliers to find the optimized variances for the trade-off. Finally, this method uses reversible data embedding to embed the recovery data and hash value for reversibility and authentication, respectively. Experimental results show the watermark visibility for test images along with the watermark transparency for different variances. Using the optimized variances, the watermarked image is at the balance between the watermark transparency and the unauthorized-user-generating noise.     

Blind quality assessment system for multimedia communications using tracing watermarking

This paper presents a novel method to blindly estimate the quality of a multimedia communication link by means of an unconventional use of digital fragile watermarking. Data hiding by digital watermarking is usually employed for multimedia copyright protection, authenticity verification, or similar purposes. However, watermarking is here adopted as a technique to provide a blind measure of the quality of service in multimedia communications. Specifically, a fragile watermark is hidden in an MPEG-like host data video transport stream using a spread-spectrum approach. Like a tracing signal, the watermark tracks the data, where it is embedded, since both the watermark and the host data follow the same communication link. The estimation of the tracing watermark allows dynamically evaluating the effective quality of the provided video services. This depends on the whole physical layer, including the employed video co/decoder. The performed method is based on the evaluation of the mean-square-error between the estimated and the actual watermarks. The proposed technique has been designed for application to wireless multimedia communication systems. According to the results obtained, the sensitivity of the detected tracing watermark on the quality of service (QoS) indices provides for some useful capabilities for analyzing future mobile Universal Mobile Telecommunications System (UMTS) services.