Yong Liang Guan

Image content authentication using pinned sine transform

Digital image content authentication addresses the problem of detecting any illegitimate modification on the content of images. To cope with this problem, a novel semifragile watermarking scheme using the pinned sine transform (PST) is presented in this paper. The watermarking system can localize the portions of a watermarked image that have been tampered maliciously with high accuracy as well as approximately recover it. In particular, the watermarking scheme is very sensitive to any texture alteration in the watermarked images. The interblock relationship introduced in the process of PST renders the watermarking scheme resistant to content cutting and pasting attacks. The watermark can still survive slight nonmalicious manipulations, which is desirable in some practical applications such as legal tenders. Simulation results demonstrated that the probability of tamper detection of this authentication scheme is higher than, and it is less sensitive to legitimate image processing operations such as compression than that of the equivalent DCT scheme.

Perception based binary image watermarking

The use of a suitable perceptual model is necessary to minimize visual distortion in marked images, because minor modifications to the pixels can be perceptible since the pixels are either black or white. In this paper, a new perceptual model is proposed for binary images that is useful for data hiding applications. In our model, the distortion that occurs after flipping a pixel is estimated on the novel curvature-weighted distance difference (CWDD) measure between two contour segments. Through subjective tests the perceptual measure is validated and highly correlated with human perception.

A new collusion attack and its performance evaluation

In this paper, we propose a new blind watermarking scheme by embedding a digital image signature/watermark in the wavelet domain and using Independent Component Analysis (ICA) technique for blind watermark extraction. The watermark is inserted in the middle frequency sub-bands. A visual masking function is used to modify the digital signature to assure the perceptual quality of the watermarked image. Independent Component Analysis (ICA) method is employed for blind watermark extraction without requiring the original image. The presented technique has been successfully evaluated and compared with other wavelet-based blind watermarking techniques against the most prominent attacks, such as JPEG and JPEG2000 compression and quantization.

Watermarking of streaming video for finger-printing applications

The rapid expansion of e-commerce and e-entertainment applications over the Internet has dramatically increased the need for copyright protection of multimedia intellectual property. Digital multimedia watermarking, defined as unperceivably embedding a secret digital code into the perceptual multimedia content, has been proposed as a major component of future copyright protection systems. Besides carrying ownership information, the embedded watermark can be made to carry client/transaction information so as to facilitate tracing of illegal re-distribution. Such form of personalised watermarking is also called finger-printing. In this paper, we propose a real-time watermarking paradigm for finger-printing streaming videos over the Internet or a private video-on-demand network. Our paradigm is based on a 3-tier architecture which runs a proxy server in between the video server and the clients video player. We adopt the proxy approach as we do not wish to modify the video server/player. The proxy server intercepts the clients request and the video data transmitted by the server, embeds a watermark into the video data based on the client/transaction information.

An Analysis of K-Connectivity in Shadowing and Nakagami Fading Wireless Multi-Hop Networks

In this paper, we develop kappa-connectivity in wireless multi-hop networks in the presence of both the log-normal shadowing and Nakagami-m fading. The formula are generally applicable in a variety of realistic physical situations. Based on the results, we are able to find the critical node density to satisfy node kappa-connectivity almost with probability 1. In addition, kappa-connectivity shows significant difference with distinct channel conditions, which necessitates a generic result. The result is useful for the design of a wireless multi-hop network in practice.

Imperceptible data embedding in sharply-contrasted binary images

Data embedding in sharply-contrasted binary images like text, drawing, signature and cartoon is a challenging issue due to simple pixel statistics in such images. Arbitrary modification to the pixels can be visually perceptible in the process of data embedding. The use of a valid perceptual model is important to minimize the effect of such visual distortion in binary images. In this paper, a novel perceptual model is used to embed significant amount of information such that the original and the marked images before and after data embedding process are perceptually similar. In our model, the distortion that occurs after flipping a pixel is estimated on the curvature-weighted distance difference (CWDD) measure between two contour segments.

Slant transform watermarking for textured images

We propose a digital watermarking algorithm based on the Slant transform for the copyright protection of complex textured images. A lot of images in practical applications, such as remote sensing and medical archiving, contain complex textures. With more AC energies concentrating in the high frequency components, images with complex textures usually suffer more from common image processing operations than smooth images do. Therefore, watermarking robustness is more an issue for textured images though it is commonly recognized that highly textured images provide more capacity for data hiding without introducing too much degradation to the visual quality of original images. Experimental results showed that our Slant transform watermarking provides significant advantage for watermarking insertion and retrieval for images with complex textures such as satellite images. An analytical comparative study on the performance of the Slant transform adapting our earlier watermarking schemes for fast Hadamard transform will be performed based on its robustness against various Stirmark and Checkmark attacks.

Improved limited path heuristic algorithm for multi-constrained qos routing

Recently limited path heuristic algorithm (LPHA) was proposed for Quality of Service (QoS) Routing with multiple constraints based on the extended Bellman-Ford algorithm. In this paper, an improved limited path heuristic algorithm (ILPHA) is introduced by means of two novel strategies, i.e., combining checking to deal with the path loss problem, and path selection to choose high-quality paths. Two path selection heuristics are recommended respectively based on the dominating area and maximal weight. Simulation results show that ILPHA can improve the performance of LPHA significantly. The comparison between the two path selection heuristics is also given.

Performance of asynchronous MC-CDMA systems with maximal ratio combining in frequency-selective fading channels

The bit error rate (BER) performance of the asynchronous uplink channel of multicarrier code division multiple access (MC-CDMA) systems with maximal ratio combining (MRC) is analyzed. The study takes into account the effects of channel path correlations in generalized frequency-selective fading channels. Closed-form BER expressions are developed for correlated Nakagami fading channels with arbitrary fading parameters. For channels with correlated Rician fading paths, the BER formula developed is in one-dimensional integration form with finite integration limits, which is also easy to evaluate. The accuracy of the derived BER formulas are verified by computer simulations. The derived BER formulas are also useful in terms of computing other system performance measures such as error floor and user capacity.

BER formulation for the blind retrieval of MPEG video watermark

A multiple watermarks embedding scheme based on multi-stage vector quantisation (VQ) is proposed. A reference watermark is generated first by referring to all the fake watermarks and the real one. Then all the watermarks except the real one are embedded into each stage of the multistage VQ system. The generated keys can be assigned to the related users to share the hidden information. Combining all the extracted watermarks, the real watermark will appear. With the fake watermarks and the structure of the multistage vector quantisation, the proposed scheme has superior features than traditional VQ-based watermarking schemes not only in security, encoding time, and codebook storage space, but also in secret sharing ability.