• Journal of Korea Multimedia Society
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• v.11 no.10
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• pp.1403-1408
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• 2008

A number of three party key exchange protocols using smart card in effort to reduce server side workload and two party password based key exchange authentication protocols has been proposed. In this paper, we introduce the survey and analysis on security vulnerability of smart card based three party authenticated key exchange protocols. Furthermore, we analyze Kwak et al's password based key exchange and authentication protocols which have shown security weakness such as Shim et al's off-line password guessing attack and propose the countermeasure to deter such attack.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.691-694
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• 2013

최근 네트워크 기술의 급속한 발전과 함께 사람들은 인터넷을 통해 다양한 서비스를 이용할 수 있다. 이러한 인터넷 환경에서 이용되는 기존 패스워드 기반의 사용자 인증은 패스워드 테이블은 요구하게 되고 패스워드 테이블 노출로 발생할 수 있는 위협들이 존재한다. 원격 사용자 인증 방식은 원격 사용자 인증 방식은 사용자의 패스워드 테이블은 요구하지 않는 인증 방식으로 스마트카드를 이용한 원격 사용자 인증에 대한 다양한 연구들이 진행되었다. 하지만, 스마트카드를 이용한 원격 사용자 인증은 통신상의 위협뿐만이 아니라 스마트카드에 저장된 정보를 통해 패스워드 추측의 위협이 발생할 수 있다. 본 연구는 해시 기반의 검증 값을 이용하여 오프라인 상에서 스마트카드에 대한 패스워드 추측 공격으로부터 안전한 방식을 제안하였다.

• Convergence Security Journal
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• v.16 no.7
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• pp.13-19
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• 2016

Recently one of the main keywords representing of Korea is O2O The O2O market is an intersection of online commerce and offline commerce. The spread and popularization of smartphones transform payment market environment from online-based(PC) to mobile-based(Smartphone) which enable payment service expanses to on/off-line both markets. Due to this movement, data security is mo vulnerable than online-based payment service but the preference of serviceability, security threat becomes bigger.O2O service expansion is now at the stage of beginning with the limited influence, but could affect to the establishment of on/off line payment system of VAN and PG in the future. However, in the moment, the motivation to destruct the system is still weak. In this research, the possibility of Non-PG mobile payment service was suggested as a new way of mobile payment service by using PG. With suggestion, it could eliminate the issues of payment method beforehand and provide low fee to merchants.

• Journal of The Korean Association of Information Education
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• v.8 no.1
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• pp.67-77
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• 2004

Recently, the rapid progress of internet technology stirs the widespread development in the educational areas. Internet has been exploited as an effective means to support school information management as well as to supplement traditional off-line teaching-learning methods. Science instruments are very important tools for science-related courses in the elementary schools. However, managing science instruments effectively has not been concerned greatly so far. Only off-line management systems were presented. In this paper, a Web-based science instrument management system is proposed. The proposed Web-based science instrument management system has the following characteristics. First, an extensive model for science instrument management is presented. The proposed model can be used as a standard model for effective management. Second, the system can provide inventory information as well as standard instrument requirements to teachers anytime anywhere. The system helps teachers make decisions on procurement plan. Finally, the user interface is designed to support easy navigation and simple use.

• The KIPS Transactions:PartA
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• v.11A no.5
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• pp.407-412
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• 2004

The e-learning system uses multimedia content for efficiency of a education and learner's convenience. With the web based e-learning, various multimedia services are difficult on account of physical factors such as network state and system performance. Also on the off line based e-learning, we have defects an insufficiency of interactions among learners and instructors, and an insufficiency of an adaptation about the latest information. In this study, we designed a multi-tier e-learning system using hybrid multimedia method, The proposed system can provide interaction and adaptability such as web based systems, and it can provide various multimedia content such as off line based systems. In experiments results, we know the proposed system improved users' convenience and an adaptability about the latest information, and interactions among learners and instructors when compare with existing e-learning system.

• Journal of Radiation Protection and Research
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• v.28 no.3
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• pp.255-261
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• 2003

An environmental radiation monitoring system based on high pressurized ionization chamber has been used for on-line gamma monitoring surrounding the KAERI (Korea Atomic Energy Research Institute), which transmits the dose data measured from ion chamber on the site via radio frequency to a central processing computer and stores the transmitted real-time data. Although communication using radio frequency has several advantages such as effective and economical transmission, storage, and data process, there is one main disadvantage that data loss during transmission often happens because of unexpected communication problems. It is possible to restore the loss data by off-line such as floppy disk but the simultaneous process and display of current data as well as the backup data are very difficult in the present on-line system. In this work, a new electronic circuit board and the operation software applicable to the conventional environmental radiation monitoring system are developed and the automatical synchronization of the ion chamber unit and the central processing computer is carried out every day. This system is automatically able to restore the backup data within 34 hours without additional equipments and also display together the current data as well as the transmitted backup data after checking time flag.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.4
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• pp.365-374
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• 1998

The SHE(Selected Harmonic Elimination) PWM scheme which eliminates specific lower order harmonics can generate h high quality output waveforms in 3-level PWM inverters. However. its application has limited since SHE switching a angles cannot be calculated on-line by a microprocessor-implemented control system. Based on off-line optimization. in which multiple SHE solutions were found and analysed for 2 to 5 switching angles per quarter in the 3-level SHE PWM pattern. this paper presents an algebraic algorithm for an ordinary microprocessor to calculate approximate SHE S switching angles on-line with such high resolution that it makes no practical difference between the accurate and the a approximate SHE switching angles. By employing the variable of the dc-link voltage Vdc' the proposed SHE PWM p pattern can ideally compensate the dc input fluctuation together with selected harmonics eliminated.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1100-1105
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• 2010

The high speed line and conventional line are a single-phase AC feeding system; and power supplies of different phases meet at SS(SubStation)s or SP(Sectioning Post)s. These sections should be negotiated with the main circuit breaker in the traction vehicle switched off, whereby the length of the neutral zone prevents the pantographs shunting adjacent overhead line section. In order for electric railway vehicles to make power running there, there must be a power supply changeover section (approx. for 1km), where a changeover switch changes a power supply to the other power supply of a train running direction sequentially. For a thorough changeover switching control, the precise train position detection is necessarily required. In this paper, to realize the ground-based train position detection method, configuration scheme of train position detection equipment is suggested by using track circuit and axle counter.

• Journal of Digital Contents Society
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• v.2 no.2
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• pp.191-197
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• 2001

The cyber university, which authoring systems for digital contents using multimedia technologies ate used for its courses, is highlighted to be a promising alternative for the current off-line education system. As the demand for the authoring system is constantly increasing, many systems, which emphasize the developers' convenience only, are currently used. Since the generated digital contents using these systems are failed to draw the learners' active interaction with contents, the new authoring system is expected to be existed. This paper presents, develops, and implements the new contents authoring system by using programing languages and/or software tools based on the storyboard. The presented, developed, and implemented system mimics the face-to-face education in off-line system, induces the users' active interaction with contents, and the effective evaluation system to the users.

• The Transactions of the Korea Information Processing Society
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• v.3 no.4
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• pp.915-925
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• 1996

In this paper, in order to find effective features which can handle variations in off-line handwritten numerals, we performed a comparative study on various sets of features. Results of experimental performance comparison shows that 4- directional features using contours and features which combined cross distance, cross, mesh and projection features are very effective for off-line handwritten numerals recognition in terms of recognition rates and recognition time. And in order to surmount limitation of recognition rate by a single neural network. we proposed a modularized neural network using majority voting and reliability factor with complex feature that mix effective features together. In order to verify the performance of the proposed method, the handwritten numeral databases of Concordia University of Canada and Dong-A University of Korea are used in the experiments. With the database of Concordia University, the recognition rate of 97.1%, the rejection rate of 1.5%, the error rate of 1.4% and the reliability of 98.5% are obtained ; and with the database of Dong-A University, there cognition rate of 98%, the rejection rate of 1.2%, the error rate of 0.8%, the reliability o99.1% are obtained.