基于直方图平移可逆水印的性能估计

多层直方图平移可逆水印算法可以获得较高的嵌入容量。由于多层嵌入复杂度较高,在实际实施多层嵌入前,一般不可预知算法是否满足用户要求的嵌入容量和水印图像质量。提出一种快速性能估计方法,该方法无需实际嵌入操作,仅根据直方图信息就可以准确估计多层嵌入后水印容量及相应的水印图像质量。实验结果表明：该方法速度快、估计精度高,为实际使用直方图平移可逆水印算法提供了一种快速、有效的判决依据。     

新的分形水印方案的研究

以基于矩的图像归一化技术及分形相关知识为基础,提出一种可有效抵抗几何攻击的数字水印新方案。方案利用归一化技术将原始图像映射到几何不变空间内,结合不变质心理论提取出归一化图像的重要区域;利用分形,通过调整DCT中频系数,将水印自适应地嵌入到重要区域的自相似块中。仿真实验结果表明,方案不仅具有较好的透明性,而且对常规信号处理和几何攻击均具有较好的鲁棒性。     

Effective watermarking scheme in the encrypted domain for buyer-seller watermarking protocol

In most watermarking schemes for copyright protection, a seller usually embeds a watermark in multimedia content to identify a buyer. When an unauthorized copy is found by the seller, the traitor’s identity can be traced by the embedded watermark. However, it incurs both repudiation issue and framing issue. To solve these problems, some buyer-seller watermarking protocols have been proposed based on watermarking scheme in the encrypted domain. In this paper, an enhanced watermarking scheme is presented. Compared with Solanki et al.’s scheme, the enhanced scheme increases effective watermarking capacity, avoids additional overhead and overcomes an inherent flaw that watermarking capacity depends on the probability distribution of input watermark sequence. Based on the security requirements of buyer-seller watermarking protocols, a new watermarking scheme in the encrypted domain with flexible watermarking capacity is proposed. It improves the robustness of watermark sequence against image compressions and enables image tampering detection. Watermark extraction is blind, which employs the same threshold criterion and secret keys as watermark embedding. Experimental results demonstrate that the enhanced watermarking scheme eliminates the drawbacks of Solanki et al.’s scheme and that the proposed watermarking scheme in the encrypted domain outperforms Kuribayashi and Tanaka’s scheme.     

Secure variable-capacity self-recovery watermarking scheme

Since existing watermarking schemes usually cannot recover the tampered position, a secure variable-capacity self-recovery watermarking scheme is proposed. Both watermark embedding capacity and security are taken into account. The original image is divided into texture blocks and smooth blocks, and the texture blocks not only save traditional information, and save the “details” information. The so-called “details” information refers to the texture information, which not only can effectively resist mean attack, but also help to improve the quality of the recovered image to meet the needs of practical work. And then according to the characteristics of different blocks, the different length compound watermarks are produced. The so-called “compound watermarks” include the authentication watermarks and information watermarks. Authentication watermarks are used to detect the tampered region, and the information watermarks which include basic watermark and additional watermark are used to recover image. Then the compound watermarks are inserted into the other blocks based on the new proposed scheme called three level secret-key embedding scheme (TLSES). And then detect the tamper blocks and recover them by the three level tamper detection scheme (TLTDS). The experimental results show that the paper can not only accurately detect the tamper region and recover image, but also can effectively resist mean attack and collage attack.

     

Adaptive reversible image watermarking scheme

This paper presents an adaptive block sized reversible image watermarking scheme. A reversible watermarking approach recovers the original image from a watermarked image after extracting the embedded watermarks. Without loss of generality, the proposed scheme segments an image of size 2^N × 2^N adaptively to blocks of size 2^L × 2^L, where L starts from a user-defined number to 1, according to their block structures. If possible, the differences between central ordered pixel and other pixels in each block are enlarged to embed watermarks. The embedded quantity is determined by the largest difference in a block and watermarks are embedded into LSB bits of above differences. Experimental results show that the proposed adaptive block size scheme has higher capacity than conventional fixed block sized method.     

Log-scaling magnitude modulated watermarking scheme

A real-time watermarking scheme with high robustness and security has been proposed based on modulating the log-scaling magnitudes of DCT coefficients, which is most suitable for JPEG images and MPEG streams. The watermark bit is encoded as the sign of the difference between the individual log-scaling magnitude of a group-region and the average one of all group-regions. The log-scaling magnitude can be modulated by modifying the low and middle frequency DCT coefficients imperceptibly. The robustness of scheme is not only dependent on those largest coefficients, but also on the other coefficients with the same proportion. It can embed 512 bits into an image with a size of 512×512, which can satisfy the payload requirement of most video watermarking applications. Moreover, the watermark embedding process only requires one-sixth of the time consumed during normal playing of video, and the watermark detection only requires one-twelfth of that, which can meet the real-time requirements of most video watermarking applications. Furthermore, the experimental results show that the presented scheme is transparent and robust to significant valumetric distortions (including additive noise, low-pass filtering, lossy compression and valumetric scaling) and a part of geometric distortions. It performs much better than the EMW algorithm in resisting all kinds of distortions except Gaussian noise with a larger deviation.     

一种水印信息可恢复的软件水印方案

针对动态图水印数据率低、水印信息遭到攻击后不易恢复的问题,提出了一种水印信息可恢复的软件水印方案。该方案结合了动态图水印和线程水印技术。为了使水印信息可恢复,在水印的嵌入过程中,利用设计的一种特殊的动态图结构表示水印信息,并在程序的线程关系中隐藏动态图的纠错码信息。提取水印图的过程中一旦检测到水印图遭到窜改,提取隐藏在程序执行时产生的线程关系中的纠错码信息,恢复被窜改的水印信息。理论分析和实验表明,该方案提高了水印的数据率,降低了程序负载,增强了水印的抗攻击性,并能在一定程度上恢复被窜改的水印信息。     

一种改进的DWT-SVD域参考水印方案

针对一类SVD域图像水印方案存在过高虚警概率的问题,提出了一种改进的混合DWT和SVD的图像参考水印算法。算法先对载体图像进行[n]层的离散小波变换,然后随机选取第[n]层的部分或全部子带形成参考子带,并对参考子带进行SVD分解;将Arnold置乱处理后的水印嵌入到SVD分解后的奇异值矩阵中。实验表明,提出的算法具有较好的透明性和安全性;与其他方案相比,解决了虚警概率问题,且对于大部分的攻击,具有更好的鲁棒性能。     

An SVD-based screen-shooting resilient watermarking scheme

Multimedia Tools and Applications - This paper proposes a new watermarking scheme that is screen-shooting resilient. We try to design a watermarking scheme that can resist the distortion generated...     

Fair billing method for VOD systems based on video quality monitoring using watermarking scheme

Multimedia Tools and Applications - The received quality of the video contents streamed over Video on Demand (VOD) networks is easily degraded by interference and other external factors during the...     

改进的动态图水印技术编码方案*

针对动态图水印性能评测指标之间相互制约的关系,寻找指标之间的平衡点,满足理想水印图的特征条件,结合现有的动态图水印技术编码方案,改进了一种编码方案。该改进方案利用二维PPCT编码纠错能力强、抗攻击性能好的特点以及K基数链表编码率高的优点,引入混合编码的思想,添加指针域,构造多个水印图,对真实水印起到混淆的作用。理论分析和实验结果表明,该改进方案提高了数据率、抗攻击能力和鲁棒性,是一种不错的水印编码方案。     

Cryptanalysis of Chu's DCT based watermarking scheme

In 2003, Chu proposed an oblivious watermarking algorithm by modifying the CKLS scheme proposed by Cox, Kilian, Leighton, and Shamoon in 1997, known as the CKLS scheme. In this correspondence, we report that the modification presented by Chu is susceptible to a suitably modified attack devised by Das and Maitra in 2004. In fact, the experimental results show that Chu's scheme is even weaker than the CKLS scheme in terms of our attack.     

Norm ratio-based audio watermarking scheme in DWT domain

In order to reach a balance between robustness, imperceptibility, and data payload, a novel blind audio watermarking scheme is proposed using the norm ratio of approximate coefficients in discrete wavelet domain (DWT). A chaotic sequence generated by Tent map is used to encrypt the watermark image and enhance the security of watermarking system. Firstly the original audio signal is segmented into non-overlapping frames and DWT is applied to each frame. Then, the approximate components are divided into two parts, and the norm ratio is calculated and modulated to embed the watermarks. Finally, the approximate components are scaled by optimizing the quality of the watermarked audio. Experimental results indicate that the proposed watermarking scheme is robust against different common attacks, such as noise addition, resampling, re-quantization, MP3 compression and amplitude scaling. The comparison analysis shows that the proposed scheme has high data payload and provides superior performance compared to the state-of-the-art watermarking schemes.     

Imperceptible digital watermarking scheme in multiple transform domains

A novel imperceptible digital watermarking scheme in multiple transform domains is presented, where the cover image is dealt with by discrete wavelet transform (DWT), discrete cosine transform (DCT) and discrete fractional random transform (DFRNT), while the watermark image is scrambled by Arnold transform and logistic map. First the watermark is scrambled by the Arnold transform, then the row and the column of the resulting watermark are scrambled by the Logistic map, respectively. In addition, four sub-band images are generated from the host image by the two-dimensional discrete wavelet transform. The low-frequency sub-band images are divided into 8?×?8 small matrices, and a coefficient matrix is produced by performing the discrete cosine transform on each matrix. An intermediate matrix with the same size as the watermark image is constructed by the intermediate frequency coefficients. Then the discrete fractional random transformation is performed on the intermediate frequency coefficient matrix and the scrambled watermark is embedded into the discrete fractional random transformation domain. Compared with the previous schemes, the proposed digital watermarking scheme has stronger imperceptibility and robustness.     

基于提升方案小波的半脆弱水印图像认证算法

在小波变换域内,将水印嵌入在特定的小波系数中,对图像带来的失真影响很小,同时可以准确地检测和篡改定位,因此目前实现认证的脆弱水印和半脆弱水印大多在小波域内.提出了一种使用提升小波变换的半脆弱水印方法.在原始宿主图像经过提升小波变换之后的低频子带,根据水印和小波系数的特征自适应地修改小波系数,嵌入过程实现了很好的不可见性和鲁棒性,实现了盲提取,并能准确地实现篡改的检测和定位.     

Owner-customer right protection mechanism using a watermarking scheme and a watermarking protocol

Over the past few years, there have been more and more robust watermarking schemes proposed for copyright protection of digital documents. The authors combine cryptography with watermarking to simultaneously address the problems of protecting the owner's copyright and the legal customer's ownership. The authors propose a robust watermarking scheme based on visual cryptography and a watermarking protocol based on asymmetric cryptography. It is worthwhile to note that the proposed schemes are resistant to counterfeit, collusion, averaging, and copy attacks, while the large majority of robust watermarking schemes are not. Furthermore, the application of digital signature and timestamp makes public verification possible.     

A robust watermarking scheme using self-reference image

In this paper, a robust watermark scheme for copyright protection is proposed. By modifying the original image in transform domain and embedding a watermark in the difference values between the original image and its reference image, the proposed scheme overcomes the weak robustness problem of embedding a watermark in the spatial domain. Besides, the watermark extraction does not require the original image so it is more practical in real application. The experimental results show that the proposed scheme provides not only good image quality, but is also robust against various attacks, such as JPEG lossy compression, filtering and noise addition.     

Performance analysis of a channel assignment scheme in cellular communication systems

In cellular communication systems, channel assignment schemes are very important to improve teletraffic performance characteristics. Because of the overlapping design of the cells in cellular communication systems, a mobile user is capable of communicating with two different bases. In this paper, a new channel assignment scheme is proposed to improve the blocking probability of a cellular communication system. The blocking probability of the cellular communication systems is analyzed based on Markov chain. According to the analytical results, the proposed channel assignment scheme shows different characteristics in comparison with fixed channel assignment scheme.