• Proceedings of the Korea Society for Simulation Conference
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• 2001.05a
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• pp.54-54
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• 2001

인터넷으로 비롯된 신경제의 큰 특징중의 하나는 계층간의 격차 (Digital Divide)이다. 이러한 계층간의 격차는 인터넷의 특성인 Winner-takes-all 현상에 의해 일어나며 이는 확률적으로 Nonlinear Polya Game을 따르는 것으로 알려져 있다. 본 논문에서는 다양한 가정하에서 Nonlinear Polya Game의 행태를 분석해 보고 Digital Divide를 최소화시키거나 제거할 수 있는 방안을 모색해 보고자 한다. 또한 이러한 분석의 경제적이고 정책적인 의미를 제시해 보고자 한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1999.06a
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• pp.1-10
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• 1999

A new digital media ear started a couple of months ago when 10 major cities in USA first boradcasted the all digital HDTV on the air. Digital video compression has been studied for decades but only recently, it becomes practical and is used in our daily life. We give an overview of the progress of video compression in recent years, particularly, the ones related to international standards. Through examples, we like to introduce this fantastic subject to the readers who were not familiar with it before.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.08a
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• pp.17-20
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• 2000

In a digital communication system, the transmission channel may introduce error into the digital signal being transmitted. It would be useful if a process could be devised so that the error could be removed in order to recover the transmitted digital signal. We design a corrective filter that is inverse filter, which will generate an output signal identical to the input signal. in order for two systems connected in cascade to produce an output which is identical to the input signal, the over-all unit sample response of the cascade connection must be a unit sample function.

• Journal of Electrical Engineering and information Science
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• v.1 no.2
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• pp.87-95
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• 1996

This paper presents a (k,n) threshold digital signature scheme with no trusted dealer. Our idea is to use the EIGamal signature scheme modified for group use. Among many digital signature schemes, our modification has a nice property for our purpose. We also show a (k.n) threshold fail stop signature scheme and two (k.n) threshold undeniable signature schemes. We use [10] as the original fail stop signature scheme, and use [3] and [2] as the original undeniable signature schemes. Since all these schemes are based on the discrete log problem, we can use the same technique.

• Journal of Internet of Things and Convergence
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• v.8 no.1
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• pp.73-78
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• 2022

Due to COVID-19, the digital transformation centered on unmanned and non-face-to-face is accelerating. Like a digital civilization, it is changing into a digital age, but for those who cannot use digital, the inconveniences in daily life are falling to the level of digital illiteracy. There is a social gap between digital users and non-users, and digital non-users are separated from society. For the digital socialization of the digitally underprivileged, the transition to the digital world is accelerating, and the ability to use digital in everyday life is becoming more important. As the transition to the digital world accelerates, individual social and economic differences are occurring. These problems are hindering the sustainable growth of society. In this study, in order to receive digital education conveniently, we intend to design an education model with excellent accessibility as an education that can be received by all citizens. It is intended to propose a digital education model that can be used universally and solve the inconvenience of life through digital comprehensive competency education that can be received step by step and can be easily received.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.1011-1025
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• 2014

A demosaicing method for a Bayer-like W-RGB color filter array (CFA) is proposed. When reproducing images from a W-RGB CFA, conventional color separation methods for W-RGB CFA are likely to cause blurring near the edges due to rough averaging using a color ratio of neighboring pixels. Moreover, these methods cannot be applied to real-life digital cameras with W-RGB CFA because the methods were proposed under an ideal situation, W=R+G+B, not a real-life situation, $W{\neq}R+G+B$. To improve edge performance, we propose a method of constant color difference assumption with inversed weight, which uses information from all edge directions for interpolating all missing color channels. The proposed method calculates the correlation between W, R, G, and B to enable its application to real-life digital cameras with W-RGB CFA. Simulations were performed to evaluate the proposed method using images captured from a real-life digital camera with W-RGB CFA. Simulation results shows that we can demosaic by using the proposed algorithm compared with the conventional one in about +34.79% SNR, +11.43% PSNR, +1.54% SSIM and 14.02% S-CIELAB error. Thus, the proposed method demosaics better than the conventional methods.

• Journal of Digital Convergence
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• v.10 no.2
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• pp.161-169
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• 2012

It requires a lot of costs and manpower to manage the election system. The electronic voting scheme is needed to make the election system to be economic and fair. Especially, wide spread use of smart phones and wireless networks makes the mobile voting is of major concern. In mobile voting scheme, a smart phone user can vote regardless of the places. In this paper, the mobile voting scheme is proposed where candidates can guarantee fairness of the election system. We analyze mobile voting requirements and create the mobile ID which has legal binding forces and PKI based digital signature keys. In the proposed scheme, a voter's ballot is signed by all candidates using undeniable multi-signature scheme. During the counting stage, the multi-signature on the ballot is not verified without help of all candidates.

• Journal of Power Electronics
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• v.18 no.5
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• pp.1523-1535
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• 2018

High-performance Phase-Locked Loops (PLLs) are critical for grid synchronization in grid-tied power electronic applications. In this paper, a new single-phase All Digital Phase-Locked Loop (ADPLL) is proposed. It features fast transient response and good robustness under distorted grid conditions. It is designed for Field Programmable Gate Array (FPGA) implementation. As a result, a high sampling frequency of 1MHz can be obtained. In addition, a new OSG is adopted to track the power frequency, improve the harmonic rejection and remove the dc offset. Unlike previous methods, it avoids extra feedback loop, which results in an enlarged system bandwidth, enhanced stability and improved dynamic performance. In this case, a new parameter optimization method with consideration of loop delay is employed to achieve a fast dynamic response and guarantee accuracy. The Phase Detector (PD) and Voltage Controlled Oscillator (VCO) are realized by a Coordinate Rotation Digital Computer (CORDIC) algorithm and a Direct Digital Synthesis (DDS) block, respectively. The whole PLL system is finally produced on a FPGA. A theoretical analysis and experiments under various distorted grid conditions, including voltage sag, phase jump, frequency step, harmonics distortion, dc offset and combined disturbances, are also presented to verify the fast dynamic response and good robustness of the ADPLL.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.7
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• pp.1537-1545
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• 2004

As the Internet continues to transform the commerce, the method of payment is one of critical components to conduct successful business across the internet. An electronic cash has all characteristics of traditional commodity cash and ensures security for all transactions. Accordingly an internet billing system based electronic cash is expected as the secure and efficient payment method in future electronic commerce. Digital Contents such as digital goods and services have the special characteristic that both the delivery of the goods and the transfer of money ran be accomplished on the same network. This allows the optimizations in the design of an electronic commerce system. In this paper, we propose an electronic payment protocol which is especially designed to purchase digital contents through internet. The proposed protocol guarantees anonymity by using a virtual ID, and minimizes payment processing steps.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.12
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• pp.6098-6122
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• 2018

Cache-based side-channel attacks have achieved more attention along with the development of cloud computing technologies. However, current host-based mitigation methods either provide bad compatibility with current cloud infrastructure, or turn out too application-specific. Besides, they are defending blindly without any knowledge of on-going attacks. In this work, we present CacheSCDefender, a framework that provides a (Virtual Machine Monitor) VMM-based comprehensive defense framework against all levels of cache attacks. In designing CacheSCDefender, we make three key contributions: (1) an attack-aware framework combining our novel dynamic remapping and traditional cache cleansing, which provides a comprehensive defense against all three cases of cache attacks that we identify in this paper; (2) a new defense method called dynamic remapping which is a developed version of random permutation and is able to deal with two cases of cache attacks; (3) formalization and quantification of security improvement and performance overhead of our defense, which can be applicable to other defense methods. We show that CacheSCDefender is practical for deployment in normal virtualized environment, while providing favorable security guarantee for virtual machines.