Yusuk Lim

Bio: Yusuk Lim is an academic researcher from University of Sydney. The author has contributed to research in topics: Audio signal processing & Speech coding. The author has an hindex of 2, co-authored 2 publications receiving 58 citations.

Web based image authentication using invisible Fragile watermark

Abstract: The demand of security is getting higher in these days due to easy reproduction of digitally created multimedia data. Digital watermark is the emerging technique to embed secret information into content for copyright protection and authentication. Watermark is embedded within an image that alteration and modification to the watermarked image can be detected in a fragile watermark system. Watermark detection is blind that does not require an original image and it is invisible to avoid revealing secret information to malicious attackers. A web based image authentication method based in digital watermarking is described in this paper. It can provide more controls to image owners and conveniences to clients who want to get authenticity of image by integrating benefits of using Internet to the watermark system.

Recovering Modified Watermarked Audio Based on Dynamic Time-Warping Technique

Abstract: An audio registration method based on dynamic timewarping (DTW) technique was described. DTW technique can be used to register two audio signals whose type of misalignment in time domain is unknown. By measuring the frame dissimilarities in two audio signals, the best alignment between a pair of audio signals can be obtained to register the two audio signals. This method can solve the registration problem for audio signal which is processed by re-scaling in the time domain. It is useful in many audio applications and has been applied in digital audio watermarking detection.

A Study on Watermarking Schemes for Image Authentication

Abstract: The digital revolution in digital image processing has made it possible to create, manipulate and transmit digital images in a simple and fast manner. The adverse affect of this is that the same image processing techniques can be used by hackers to tamper with any image and use it illegally. This has made digital image safety and integrity the top prioritized issue in today’s information explosion. Watermarking is a popular technique that is used for copyright protection and authentication. This paper presents an overview of the various concepts and research works in the field of image watermark authentication. In particular, the concept of content-based image watermarking is reviewed in details. KeywordsWatermark Lifecycle, Robust Watermarking Schemes, Fragile Watermarking Schemes, HVS, ICA.

Medical Image Authentication through Watermarking Preserving ROI

Abstract: Telemedicine is a well-known application where enormous amount of medical data need to be securely transferred over the public network and manipulate effectively. Medical image watermarking is an appropriate method used for enhancing security and authentication of medical data, which is crucial and used for further diagnosis and reference. This project focuses on the study of medical image watermarking methods for protecting and authenticating medical data. Additionally, it covers algorithm for application of water marking technique on Region of Non Interest (RONI) of the medical image preserving Region of Interest (ROI). The medical images can be transferred securely by embedding watermarks in RONI allowing verification of the legitimate changes at the receiving end without affecting ROI. Segmentation plays an important role in medical image processing for separating the ROI from medical image. The proposed system separate the ROI from medical image by GUI based approach, which works for all types of medical images. The experimental results show the satisfactory performance of the system to authenticate the medical images preserving ROI.

Reversible dynamic secure steganography for medical image using graph coloring

Abstract: Securing data in telemedicine applications is extremely essential and therefore it is mandatory to develop algorithms which preserve the data transmitted. Steganography (information hiding technique) plays a crucial role in telemedicine applications by providing confidentiality, integrity, availability and authenticity. This paper proposes a novel steganography technique that conceals patient information inside a medical image using a dynamic key generated by graph 3 coloring problem. The proposed method ensures reversibility as the original medical image is restored after extracting the embedded data from the stego medical image. Despite the embedding of patient information in the medical image, the visual quality of the image is preserved. Experimental results show that the proposed method is resistant against uniform affine transformations such as cropping, rotation and scaling. The proposed method is designed by considering issues related to transmission errors which could contaminate the medical images transmitted. The performance of the proposed method is compared to other information hiding methods against various parameters such as robustness of stego-image against affine transformations, toughness of the dynamic key generated, detection of transmission error, embedding rate and reversibility.

Watermarking of Medical Images for Content Authentication and Copyright Protection

Abstract: Due to development of latest technologies in the areas of communication and computer networks, present businesses are moving to the digital world for e ectiveness, convenience and security. One of the examples is in the area of medical applications, where traditional diagnosis is being replaced by e-diagnosis. This paradigm gave birth to number of applications in healthcare industry like teleconsulting, telesurgery and telediagnosis. All these applications require the exchange of medical images in digital format from one geographical location to another throughout the globe via a cheap and fast network such as Internet. However, digital form of medical image can easily be manipulated through image processing softwares.Insurance companies, hospitals as well as patients might want to modify the medical images for a number of reasons. The tampered images may be used for illegal purposes. The objective of this dissertation is to investigate how to protect a medical images, detect tampered images and recover the original image using the technique of Digital Watermarking. Watermarking tech- nology can be categorized into robust, fragile and semi-fragile watermarking, each serving for di erent purposes. In order to facilitate sharing and remote handling of medical images, we propose techniques to solve the problem of copyright protection and content authentication using robust and fragile watermarking respectively. In the rst part of this dissertation, we design a fragile watermarking system for the exact authentication of medical images. The proposed system authenticates the computed tomography (CT) scan medical images of thorax area against di erent distortions. The system rst enhances the embedding capacity of a CT scan image by isolating the actual lung parenchyma unlike classical watermarking techniques, which use logical square or ellipse for isolating region of interest (ROI). Secondly it embeds watermark only in region of non interest (RONI), thus not compromising the diagnosis value of medical image. The method utilizes the spatial domain watermarking and least signi cant bit (LSB) replacement method for embedding the watermark. Experimental results reveal that the proposed system detects both legitimate and illegitimate distortions. Robust watermarks are well suited for copyright protection because they stay intact with the image under various manipulations. In the second part of the dissertation, we investigate an approach of robust watermarking for protection of medical images which ensures the security of medical images against geomet- rical distortions. In the proposed method we rstly normalize the medical image using image moments in order to make it invariant against geometric transformations. Secondly, we select the salient regions in the normalized image based on feature points detected by Harris corner detector. Watermarking is performed in Discrete Cosine Transform (DCT) domain of salient regions by adapting block based embedding. The scheme is completely blind, that it does not require the original image to detect the watermark. We thus address the issue of tolerating a ne transformations in medical images that is hardly be found in existing schemes of medical image watermarking. In third part of the dissertation, we investigate the complete reversible watermarking system. The proposed method uses integer wavelet transform and companding technique which can embed and recover the secret information as well as can restore the image to its pristine state. The method takes advantage of block based watermarking and iterative optimization of threshold for companding, which avoids histogram pre and post-processing. Consequently, it reduces the associated overhead usually required in most of the reversible watermarking techniques. As a result, it keeps the distortion small between the marked and the original images. Experimental results show that the proposed method outperforms the existing reversible data hiding schemes reported in the literature.