Po-Chyi Su

Wavelet-based digital image watermarking.

A wavelet-based watermark casting scheme and a blind watermark retrieval technique are investigated in this research. An adaptive watermark casting method is developed to first determine significant wavelet subbands and then select a couple of significant wavelet coefficients in these subbands to embed watermarks. A blind watermark retrieval technique that can detect the embedded watermark without the help from the original image is proposed. Experimental results show that the embedded watermark is robust against various signal processing and compression attacks.

Steganography in JPEG2000 compressed images

Information hiding in JPEG2000 compressed images is investigated in this research. The challenges of covert communication in this state-of-the-art image codec are analyzed and a steganographic scheme is then proposed to reliably embed high-volume data into the JPEG2000 bit-stream. A special mode of JPEG2000 is employed, and its usage and functions are explained and justified. Experimental results are given to demonstrate the performance of the proposed algorithm.

Robust and efficient digital audio watermarking using audio content analysis

Digital audio watermarking embeds inaudible information into digital audio data for the purposes of copyright protection, ownership verification, covert communication, and/or auxiliary data carrying. In this paper, we first describe the desirable characteristics of digital audio watermarks. Previous work on audio watermarking, which has primarily focused on the inaudibility of the embedded watermark and its robustness against attacks such as compression and noise, is then reviewed. In this research, special attention is paid to the synchronization attack caused by casual audio editing or malicious random cropping, which is a low-cost yet effective attack to watermarking algorithms developed before. A digital audio watermarking scheme of low complexity is proposed in this research as an effective way to deter users from misusing or illegally distributing audio data. The proposed scheme is based on audio content analysis using the wavelet filterbank while the watermark is embedded in the Fourier transform domain. A blind watermark detection technique is developed to identify the embedded watermark under various types of attacks.

An Integrated Approach to Image Watermarking and JPEG-2000 Compression

A scheme which integrates image compression and image watermarking in an effective way is proposed in this research. The image compression scheme under consideration is EBCOT (Embedded Block Coding with Optimized Truncation) which has been adopted in the verification model (VM) of the emerging JPEG-2000 image compression standard. The watermark is embedded during the process when the compressed bit-stream is formed, and can be detected on the fly in image decoding. Thus, watermark embedding and retrieval can be done very efficiently in comparison with other existing watermarking schemes. In addition to efficiency, the proposed scheme has many interesting features. The embedded watermark is robust against various signal processing attacks such as coding and filtering while the watermarked image maintains good perceptual quality. The watermark retrieval procedure does not require the knowledge of the original image. Furthermore, the watermark can be detected progressively and region of interest (ROI) watermarking can be accomplished easily.

Blind digital watermarking for cartoon and map images

Cartoon/map images are synthetic graphics without complicated color and texture variation, which makes the embedding of invisible and robust digital watermarks difficult. In this research, we propose wavelet-based, threshold-adaptive watermarking scheme (TAWS) which can embed invisible robust watermarks into various kinds of graphical images. TAWS selects significant subbands and inserts watermarks in selected significant coefficients. The inserted watermarks are adaptively scaled by different threshold values to maintain the perceptual integrity of watermarked images and achieve robustness against compression and signal processing attacks. Another major contribution of this work is that the cast watermark is retrieved without the knowledge of the original image. The so-called blind watermark retrieval technique is very useful in managing a large cartoon, trademark and digital map databases. Finally, a company logo that clearly identifies the copyright information can be embedded in cartoon and map images without serious perceptual loss. Experimental results are given to demonstrate the superior performance of TAWS.

Robust audio watermarking for copyright protection

A digital audio watermarking scheme of low complexity is proposed in this research as an effective way to deter users from misusing or illegally distributing audio data. Previous work on audio watermarking has primarily focused on the inaudibility of the embedded watermark and its robustness against attacks such as compression and noise. In this research, special attention is paid to the synchronization attack caused by casual audio editing or malicious random cropping, which is a low-cost yet effective attack to watermarking algorithms developed before. The proposed scheme is based on audio content analysis and watermark embedding in the Fourier transform domain. A blind watermark detection technique is developed to identify the embedded watermark under various types of attacks.

Data embedding for vector quantization image processing on the basis of adjoining state-codebook mapping

Information hiding for images is an important research issue in digital multimedia. It provides a way to certify copyrights of image files, as well as a means of secret communication for people. In this paper, we propose a reversible image information hiding scheme based on vector quantization (VQ). The proposed scheme uses a new technique called Adjoining State-Codebook Mapping (ASCM) to map the content of an image block to an index in the corresponding state-codebooks. The ASCM technique uses two adjacent image blocks of an encoding image block to create two state-codebooks, which can represent the encoding image block more accurately. Therefore, it can reduce the size of the output code-stream and yet still provide large embedding capacity for secret data. Experimental results indicate that the proposed scheme has better compression bit rate and larger embedding capacity when we compare the proposed scheme with recent similar studies, proposed by Chang et al. in 2009 and Yang et al. in 2011 respectively.

A practical design of digital video watermarking in H.264/AVC for content authentication

In this research, we propose a practical digital video watermarking scheme mainly used for authenticating the H.264/AVC compressed videos to ensure their correct content order. The watermark signals, which represent the serial numbers of video segments, are embedded into nonzero quantization indices of frames to achieve both the effectiveness of watermarking and the compact data size. The human visual characteristics are taken into account to guarantee the imperceptibility of watermark signals and to attain an efficient implementation in H.264/AVC. The issues of synchronized watermark detections are settled by selecting the shot-change frames for calculating the distortion-resilient hash, which helps to determine the watermark sequence. The experimental results demonstrate the feasibility of the proposed scheme as the embedded watermarks can survive the allowed transcoding processes while the edited segments in the tampered video can be located.

Geometrically Resilient Digital Image Watermarking by Using Interest Point Extraction and Extended Pilot Signals

A feature-based digital image watermarking scheme is proposed to resist geometrical transformations. Such interest point extraction as scale-invariant feature transform is applied to form the invariant regions for signal embedding. Along with the watermark, the pilot signal used for synchronized detection will also be embedded to help to determine larger areas for improving the payload of watermarking and/or increasing the confidence of watermark detection. Both embedded signals are weighted by the just noticeable difference of Watsons perceptual model to meet the requirement of invisibility. In the detection phase, after the same interest point extraction, synchronization can be achieved via adjusting the related affine parameters of grids on the investigated image to detect the possible hidden pilot signal so that the watermark can be successfully retrieved afterward. Experimental results show the feasibility of the proposed method.

Towards Effective Content Authentication for Digital Videos by Employing Feature Extraction and Quantization

A content authentication scheme for digital videos is proposed in this paper. In order to prevent the content from being unnoticeably tampered with by using digital editing facilities, we employ the approach of scalar/vector quantization on the reliable features extracted from video frame blocks to form the authentication code, which is transmitted along with the video. The resulting authentication code is sensitive to malicious modifications of video data but resilient to allowed lossy compression processes, such as H.264/advanced video coding (AVC). The integrity of video content can thus be guaranteed if the extracted feature matches the transmitted authentication code. Experimental results will show the feasibility of the proposed scheme.