Choong-Hoon Lee

Korea Advanced Institute of Science and Technology , Seoul, Seoul, South Korea

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Publications (13)6.71 Total impact

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    Hae-Yeoun Lee, Choong-Hoon Lee, Heung-Kyu Lee
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    ABSTRACT: This paper addresses a geometrically invariant watermarking method for digital images. Most previous watermarking algorithms perform weakly against geometric distortions, which desynchronize the location for the inserted watermark. Watermark synchronization, which is a process for finding the location for watermark insertion and detection, is crucial for robust watermarking. In this paper, we propose a watermarking method that is robust to geometric distortions. In order to synchronize the location for watermark insertion and detection, we use circular Hough transform, which extracts circular features that are invariant to geometric distortions. The circular features are then watermarked using additive way on the spatial domain. Our method belongs to the category of blind watermarking techniques, because we do not need the original image during detection. Experimental results support the contention that our method is useful and considerably robust against both geometric distortion attacks and signal processing attacks as listed in Stirmark 3.1.
    Multimedia Tools and Applications 01/2007; 34:337-353. · 1.01 Impact Factor
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    ABSTRACT: This paper addresses an effective technique for digital fingerprinting for video. The code modulation technique, that uses an averaging collusion resilient fingerprint code derived from BIBD, is a robust method against averaging attacks. In this paper, we propose a new fingerprint code based on GD-PBIBD theory that is efficient in designing the fingerprint code and describe an effective method to embed and detect the fingerprint code, in which the merits of orthogonal modulation and coded modulation techniques are combined. To analyze the performance, we apply our method to video applications using a spread-spectrum watermarking technique in the spatial domain and the results show the proposed method is effective for fingerprint code embedding and detection.
    Circuits and Systems, 2005. ISCAS 2005. IEEE International Symposium on; 06/2005
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    Choong-Hoon Lee, Heung-Kyu Lee
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    ABSTRACT: In this paper, we propose an autocorrelation function (ACF) based watermarking scheme in the discrete wavelet transform (DWT) domain. Conventional ACF-based watermarking embeds a watermark in the spatial domain due to its detection mechanism.We show that the autocorrelation (AC) peaks, which play an important role in estimating the applied geometric attacks in ACF-based watermarking, can also be extracted by embedding the watermark in the DWT domain. In the proposed scheme, a periodic watermark is embedded in the DWT domain by considering the AC peak strength and noise visibility. The proposed scheme also deals efficiently with the image shift problem in the detection process by using the undecimated DWT. Experimental results show that the proposed scheme yields stronger AC peaks than the spatial domain scheme does and, as a result, shows improved robustness against combined geometric-removal.
    Optics Express 03/2005; 13(4):1307-21. · 3.55 Impact Factor
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    Choong-Hoon Lee, Heung-Kyu Lee
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    ABSTRACT: We propose an improved autocorrelation function (ACF)- based image watermarking that is robust to combined geometric and removal attacks. ACF-based watermarking is thought of as one of the most effective watermarking schemes that resist geometric attacks. In this watermarking scheme, the autocorrelation peaks of the watermark play an important role for geometric attack estima- tion. The peaks, however, are vulnerable to attacks. The proposed scheme enhances the performance of ACF-based watermarking by improving the strength of the peaks. The information of an original image is used at the embedding time, so that the detector can ex- tract strong autocorrelation peaks. Experimental results show that the proposed scheme yields better robustness than conventional ACF based watermarking against combined geometric-removal at- tacks. © 2005 SPIE and IS&T. (DOI: 10.1117/1.1868000)
    Journal of Electronic Imaging 01/2005; 14:013012. · 1.06 Impact Factor
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    Hae-Yeoun Lee, Choong-Hoon Lee, Heung-Kyu Lee, Jeho Nam
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    ABSTRACT: This paper addresses feature-based image watermarking methods for digital contents. Most previous watermarking algorithms suffer from geometric distortion attacks that desynchronize the location of the inserted watermark. In order to synchronize the watermark location, watermark synchronization should be performed. One solution for watermark synchronization is to use image fea- tures. This paper describes a feature-based watermarking method based on scale-invariant keypoints. We extract feature points from the scale-invariant keypoint extractor and then decompose feature points into a set of disjoint tri- angles. These triangles are watermarked by an additive spread-spectrum method on the spatial domain. We perform an intensive simulation in comparison with other feature-based watermarking methods using 100 test images. Results show that the proposed method is considerably robust against both geometric distor- tion attacks and signal processing attacks listed in Stirmark 3.1.
    Advances in Multimedia Information Processing - PCM 2005, 6th Pacific-Rim Conference on Multimedia, Jeju Island, Korea, November 13-16, 2005, Proceedings, Part II; 01/2005
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    Choong-Hoon Lee, Heung-Kyu Lee, Youngho Suh
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    ABSTRACT: In this paper, we propose an improved autocorrelation function (ACF) based watermarking. The autocorrelation function based watermarking has been known to be one of the effective watermarking schemes that are resilient to geometric transform attacks. In this watermarking scheme, both the peaks in the autocorrelation function of a marked image and the embedded watermark should survive after various attacks. Generally, the autocorrelation peaks are less robust than the actual watermark signal. The main focus of this paper is the improvement of the robustness of the peaks in an autocorrelation function. Since an original image and the detector structure are available at the embedding time, instead of simple addition of a watermark to an image, the watermark embedder analyzes the original image and uses this information actively during the embedding process so that the marked image has higher periodic autocorrelation peaks. The proposed watermarking scheme has higher robustness than a conventional ACF based watermarking against geometric attacks that are combined with removal attacks.
    Proc SPIE 06/2003;
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    Jiang Du, Choong-Hoon Lee, Heung-Kyu Lee, Youngho Suh
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    ABSTRACT: Digital watermarking is an enabling technology to prove ownership on copyrighted material, detect originators of illegally made copies, monitor the usage of copyrighted multimedia data, and analyze the spread spectrum of data over networks and servers. Most watermarking methods for images and video can be viewed as a communications problem in which the watermark must be transmitted and received through a watermark channel. This channel includes distortions resulting from attacks and interference from the original digital data. It is well accepted that an effective watermarking scheme may be described as the secure, imperceptible, robust communication of information by direct embedding in, and retrieval from, digital data. For verifying the security and robustness of watermarking algorithms, specific attacks have to be applied to test them. By using a theoretical approach based on random processes, signal processes, and communication theory, we propose a stochastic formulation of a new watermarking attack using a blind source separation-based concept. The proposed attack considers the watermarking channel as a "black-box". A host image was passed through the "black-box", which includes the watermarking embedding process, and then the watermarked image was produced The watermarked image is viewed as linear mixtures of unknown source signals, and we attempt to recover sources from their linear mixtures without resorting to any prior knowledge by using blind source separation theory.
    Multimedia Software Engineering, 2002. Proceedings. Fourth International Symposium on; 02/2002
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    ABSTRACT: In this paper, we present a method for protection of digital contents by using the watermark embedding in special object, especially, human faces. To insert the watermark signals that are composed of noise like binary signals, we first localize the face regions within images by using the color and edge information. The skin color area is filtered out and then edge detector is applied for skin area to find out face features. These features are used for decision whether the skin area is face region or not. The face region is divide non-overlapping sub-blocks and a watermark bit is inserted into the each sub- block by considering the block activity. We insert a watermark bit in DCT domain of each sub-block. The level of modification of the DCT coefficients is determined considering the block variance. The non-zero coefficients of the DCT are selected and modified according to the robustness levels. Then, inverse DCT is performed. The extraction of the watermark is performed by comparing the original image in DCT domain. The robustness of the watermarking is similar to the other methods in DCT, but it has good visual qualities and less intended external piracy in terms of psychology.
    Proc SPIE 05/2000;
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    Choong-Hoon Lee, Hwarig-Seok Oh, Heung-Kyu Lee
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    ABSTRACT: This paper presents an adaptive video watermarking using motion information. Because video data have one more dimension than image data, simple adaptation of image watermarking method to video data would reveal some types of visual artifact such as flickering. In the proposed scheme, same watermark information is embedded for same region in each frame to decrease such visual artifact. For higher robustness and invisibility, watermarking strength is adjusted by motion information and region complexity.
    Proc SPIE 01/2000; 3971:209-216.
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    ABSTRACT: The motion estimation and compensation technique is widely used for video coding applications but the real-time motion estimation is not easy due to its enormous computations. In this paper, a new adaptive reduction of search area for the block-matching algorithm is presented to reduce the computational complexity of the full search block-matching algorithm for low bit-rate video coding. The proposed method exploits the correlation of successive video frames and adjusts the size of search area depending on the displaced block difference and the block classification information of the block in the previous frame. Simulation results show that the proposed algorithm has similar mean square error performance to the full search block-matching algorithm but only requires less a half computational complexity than the full search algorithm
    IEEE Transactions on Consumer Electronics 09/1999; · 1.09 Impact Factor
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    ABSTRACT: An adaptive digital image watermarking system considering of the human visual system (HVS) is presented in the frequency domain. The digital watermarks are embedded in selected discrete cosine transform (DCT) coefficients of variable size of blocks. To accommodate the HVS characteristics, the image is divided into variable size of blocks, where each block contains only homogeneous regions. The watermark is inserted by significantly changing the selected DCT coefficients of the block that has great variance or by slightly changing for the stationary block. It is shown that the proposed method has good robustness against several image processing operations without significant degradation of image quality by simulation using various test images
    TENCON 99. Proceedings of the IEEE Region 10 Conference; 02/1999
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    ABSTRACT: Persistent Association Technology associates the meta-data with the contents persistently. In MPEG-21 architec-ture, one of promise multimedia framework for ubiqui-tous environment, multimedia contents are distributed with its metadata. The metadata are widely used for dis-tribution, surveillance, and protection of multimedia con-tents in multimedia framework. In order to provide more secure multimedia services, the PAT is indispensable. The morphology of ubiquitous multimedia is different from ordinary multimedia. Moreover ubiquitous network environments have a mixture network of several wire and/or wireless. Ubiquitous multimedia challenges to current multimedia technologies. Several technical issues on the PAT for ubiquitous multimedia are discussed in this paper. We propose that a scalable form of PAT is one of feasible solution.
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    Jiang Du, Choong-Hoon Lee, Heung-Kyu Lee, Youngho Suh
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    ABSTRACT: With the rapid growth of multimedia application, there has been significantly bared a crucial need for effective copyright protection mechanisms. Therefore, digital image, video, audio and text watermarking has recently become a very active research area of signal and information processing, as a solution to this problem. Many important issues have been pointed out, one of them being the robustness to non-intentional and intentional attacks. In this paper, a new estimation based watermark attack method is presented. The proposed attack regards the watermark system as a black box by assuming watermark signal as different kinds of noise, instead of using the prior knowledge of the watermark signal and embedding methods. To estimate the original image data, blind estimation and a MIMO linear channel are introduced. Experimental results demonstrate the proposed watermark attack method show the high efficiency against known academic and commercial methods. The watermark is completely destroyed in all tested images without altering the image quality.