Anthony T. S. Ho

A hybrid watermarking scheme for H.264/AVC video

A novel H.264/AVC watermarking method is proposed in this paper. By embedding the robust watermark into DCT domain and the fragile watermark into motion vectors respectively, the proposed method can jointly achieve both copyright protection and authentication. Our scheme outperforms other video watermarking schemes on higher watermarking capacity especially in lower compression bit-rates. Furthermore, being well aligned with Lagrangian optimization for mode choice featured in H.264/AVC, the proposed scheme only introduces small distortions into the video content. Experimental results also demonstrate that the proposed solution is very computationally efficient during watermark extraction.

Robust Video Watermarking of H.264/AVC

A robust video watermarking scheme of the state-of-the-art video coding standard H.264/AVC is proposed in this brief. 2-D 8-bit watermarks such as detailed company trademarks or logos can be used as inconvertible watermark for copyright protection. A grayscale watermark pattern is first modified to accommodate the H.264/AVC computational constraints, and then embedded into video data in the compressed domain. With the proposed method, the video watermarking scheme can achieve high robustness and good visual quality without increasing the overall bit-rate. Experimental results show that our algorithm can robustly survive transcoding process and strong common signal processing attacks, such as bit-rate reduction, Gaussian filtering and contrast enhancement

A new semi-fragile image watermarking with robust tampering restoration using irregular sampling

This paper presents a semi-fragile watermarking method for the automatic authentication and restoration of the content of digital images. Semi-fragile watermarks are embedded into the original image, which reflect local malicious tampering on the image. When tampered blocks are detected, the restoration problem is formulated as an irregular sampling problem. These blocks are then reconstructed, making use of the information embedded in the same watermarked image, through iterative projections onto convex sets. In contrast to previous methods, the restoration process is robust to common image processing operations such as lossy transcoding and image filtering. Simulation results showed that the scheme keeps the probability of false alarm to a minimum while maintaining the data integrity of the restored images.

Detection of Face Spoofing Using Visual Dynamics

Rendering a face recognition system robust is vital in order to safeguard it against spoof attacks carried out using printed pictures of a victim (also known as print attack) or a replayed video of the person (replay attack). A key property in distinguishing a live, valid access from printed media or replayed videos is by exploiting the information dynamics of the video content, such as blinking eyes, moving lips, and facial dynamics. We advance the state of the art in facial antispoofing by applying a recently developed algorithm called dynamic mode decomposition (DMD) as a general purpose, entirely data-driven approach to capture the above liveness cues. We propose a classification pipeline consisting of DMD, local binary patterns (LBPs), and support vector machines (SVMs) with a histogram intersection kernel. A unique property of DMD is its ability to conveniently represent the temporal information of the entire video as a single image with the same dimensions as those images contained in the video. The pipeline of DMD + LBP + SVM proves to be efficient, convenient to use, and effective. In fact only the spatial configuration for LBP needs to be tuned. The effectiveness of the methodology was demonstrated using three publicly available databases: (1) print-attack; (2) replay-attack; and (3) CASIA-FASD, attaining comparable results with the state of the art, following the respective published experimental protocols.

Multiple Band-Notched UWB Antenna With Band-Rejected Elements Integrated in the Feed Line

To mitigate potential interferences with coexisting wireless systems operating over 3.3-3.6 GHz, 5.15-5.35 GHz, or 5.725-5.825 GHz bands, four novel band-notched antennas suitable for ultra-wideband (UWB) applications are proposed. These include UWB antennas with a single wide notched band, a single narrow notched band, dual notched bands, and triple notched bands. Each antenna comprises a half-circle shaped patch with an open rectangular slot and a half-circle shaped ground plane. Good band-notched performance is achieved by using high permittivity and low dielectric loss substrate, and inserting quarter-wavelength horizontal/vertical stubs or alternatively embedding quarter-wavelength open-ended slots within the feed line. The results of both simulation and measurement confirm that the gain suppression of the single and multiple band-notched antennas in each desired notched band are over 15 dB and 10 dB , respectively. The radiation pattern of the proposed triple band-notched design is relatively stable across the operating frequency band.

Digital image-in-image watermarking for copyright protection of satellite images using the fast Hadamard transform

In this paper, a robust and efficient digital image watermarking algorithm using the fast Hadamard transform (FFIT) is proposed for the copyright protection of satellite images. This algorithm can embed or hide an entire image or pattern as a watermark such as a companys logo or trademark directly into the original satellite image. The performance of the proposed algorithm is evaluated using a benchmarking tool called Stirmark. Results show that this algorithm is very robust and can survive up to 60% of all Stirmark attacks. These attacks were tested on a number of satellite test images of size 512/spl times/512/spl times/8 bit, embedded with a watermark image of size 64/spl times/64/spl times/8 bits. The simplicity of the fast Hadamard transform also offers a significant advantage in shorter processing time and ease of hardware implementation.

LOW-PROFILE DIRECTIONAL ULTRA-WIDEBAND ANTENNA FOR SEE-THROUGH-WALL IMAGING APPLICATIONS

A compact-size planar antenna with ultra-wideband (UWB) bandwidth and directional patterns is presented. The antenna can be fabricated on a printed circuit board (PCB). On one side of the PCB, it has a circular patch, and on the other side it has a slot-embedded ground plane with a fork-shaped feeding stub in the slot. Directional radiation is achieved by using a reflector below the antenna. To reduce the thickness of the antenna, a new low-profile antenna configuration is proposed. Three types of directional UWB antennas are analyzed. The distance between the antenna and the reflector is 12 mm (0.16 λ0, λ0 is the free space wavelength at the lowest frequency). In order to validate the design, a prototype is also fabricated and measured. Measured results agree well with the simulated ones. The measured results confirm that the proposed antenna features a reflection coefficient below -10 dB over the UWB range from 4.2 GHz to 8.5 GHz, a maximum gain around 9 dBi, a front-to-back ratio over 17 dB and pulse fidelity higher than 90% in the time domain. Thus it is promising for see-through-wall imaging applications.

Fragile Watermarking Based on Encoding of the Zeroes of the

In this paper, a new fragile watermarking method for digital image authentication is proposed based on the zero locations of the z-transform. The z-transform domain is a new transform space for fragile watermark embedding. Our watermarking method is designed by exploiting the sensitivity of the positions of the zeroes of the z-transform around the unit circle to any change made on the host image. The watermarking system can localize the portions of a watermarked image that have been tampered with with high accuracy. In addition, the newly proposed scheme is more secure than normal least-significant bits-based fragile watermarking techniques. Experimental results as well as the theoretical analysis demonstrated the fragility and accuracy of the new method.

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In this paper, a robust and efficient digital image watermarking algorithm using the fast Hadamard transform (FHT) is proposed for the copyright protection of digital images. This algorithm can embed or hide an entire image or pattern as a watermark such as a companys logo or trademark directly into the original image. The performance of the proposed algorithm is evaluated using Stirmark 3.1 that consists of 90 different types of image attacks. Results show that this algorithm is very robust and can survive most of the Stirmark attacks. These attacks were tested on a number of test images of size 512/spl times/512/spl times/8 bits, embedded with a watermark image of size 64/spl times/64/spl times/8 bits. The simplicity of the fast Hadamard transform also offers a significant advantage in shorter processing time and ease of hardware implementation than other orthogonal transforms, such as the discrete cosine transform and wavelet transform.

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A novel planar ultra-wideband (UWB) antenna with dual band-notched characteristics is proposed. The antenna is fabricated on a printed circuit board (PCB), having a circular monopole and arc-shaped parasitic strips on one side and a ground plane with a slot aperture on the other side. Two narrow bands at 5.15-5.35 GHz and 5.725-5.825 GHz are notched by using two arc-shaped parasitic strips on the same layer of the radiator. Compared with other band-notched UWB antennas, the proposed antenna exhibits the advantages of simple structure, compact size, simple control of each notched frequency band using separate parasitic strips, and good performance. Surface current distributions and equivalent circuit model are applied to analyze the operating principle of the proposed antenna. To validate the concept, a prototype is fabricated and tested. Both simulated and measured results confirm that the proposed antenna achieves a wide bandwidth from 3.1 GHz to 10.6 GHz with two narrow bands notched successfully. The results of VSWR, radiation patterns and gain response are shown and discussed in detail. The antenna enables the independent control of the notched frequency bands, and the proposed method can be extended for designing planar UWB antennas with multiple band-notched characteristics and reconfigurable notched frequency.