• 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 KIEE Conference
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• 2005.07a
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• pp.6-8
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• 2005

본 논문은 제2차 전력수급기본계획을 토대로 2006년부터 2017년도까지 중장기 전력계통의 운영 전망을 분석하였다. 주요 내용으로는 2006년, 2008년, 2010년, 2012년 2017년도에 대한 지역별 전력수급전망, 송전망 조류추이, 고장용량 분석, 조상설비 필요량, 계통전압안정도, 수도권 융통전력한계, 과도안정도 분석 등을 다루고 있으며 본 전력계통 운영전망에 관한 검토내용은 향후 전력계통 운영 및 제3차 전력수급기본계획(발전 및 송전설비계획 부분) 수립에 활용될 예정이다.

• Journal of Communications and Networks
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• v.8 no.4
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• pp.461-474
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• 2006

A group key exchange protocol is a cryptographic primitive that describes how a group of parties communicating over a public network can come up with a common secret key. Due to its significance both in network security and cryptography, the design of secure and efficient group key exchange protocols has attracted many researchers' attention over the years. However, despite all the efforts undertaken, there seems to have been no previous systematic look at the growing problem of key exchange over combined wired and wireless networks which consist of both stationary computers with sufficient computational capabilities and mobile devices with relatively restricted computing resources. In this paper, we present the first group key exchange protocol that is specifically designed to be well suited for this rapidly expanding network environment. Our construction meets simplicity, efficiency, and strong notions of security.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.12
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• pp.5135-5149
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• 2015

Communications among multi-party must be fast, cost effective and secure. Today's computing environments such as internet conference, multi-user games and many more applications involve multi-party. All participants together establish a common session key to enable multi-party and secure exchange of messages. Multi-party password-based authenticated key exchange scheme allows users to communicate securely over an insecure network by using easy-to-remember password. Kwon et al. proposed a practical three-party password-based authenticated key exchange (3-PAKE) scheme to allow two users to establish a session key through a server without pre-sharing a password between users. However, Kwon et al.'s scheme cannot meet the security requirements of key authentication, key confirmation and anonymity. In this paper, we present a novel, simple and efficient multi-party password-based authenticated key exchange (M-PAKE) scheme based on the elliptic curve cryptography for mobile environment. Our proposed scheme only requires two round-messages. Furthermore, the proposed scheme not only satisfies security requirements for PAKE scheme but also achieves efficient computation and communication.

• KDI Journal of Economic Policy
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• v.37 no.4
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• pp.1-20
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• 2015

We examine the validity of popular exchange rate models such as the purchasing power parity (PPP) hypothesis and the monetary model for Korean won/US dollar exchange rate. Various specification tests demonstrate that Korean data are more favorable for both models based on time-varying cointegration coefficients as compared to those based on constant cointegration coefficients. When the abilities to predict future exchange rates between those models based on time-varying cointegration coefficients are compared, an in-sample analysis shows that the time-varying PPP (monetary model) has better predictive power over horizons shorter (longer) than one year. Results from an out-of-sample analysis indicate that the time-varying PPP outperforms models based on constant cointegration coefficients when predicting future exchange rate changes in the long run.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.227-228
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• 2015

DTS(Dispatcher Training Simulator)는 EMS(Energy Management System) 전력계통 모델을 기반으로 off-line 환경에서 운영되는 급전원 훈련용 시뮬레이터이다. 전력거래소 중앙전력관제센터는 DTS를 이용하여 다양한 상황별 고장복구 훈련을 시행하고 있으며, 계통 검토 검증에도 활용하고 있다. 본 논문은 DTS를 활용하여 육지계통 UFR 동작과 광역정전 발생을 모의하고, 그에 따른 전력계통 변화와 정상운영 조치 시뮬레이션 결과에 대해 소개하고자 한다.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2002.11a
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• pp.423-431
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• 2002

본 연구에서는 웹 서비스 기술을 이용하여 B2B Exchange 구현을 위한 프레임웍을 설계하고 XML과 SOAP기술을 이용하여 이를 구현하였다. B2B e-Commerce가 주도적인 회사 중심의 B2B인데 반해서 B2H Exchange는 다수의 구매자와 판매자가 하나의 가상 시장에서 역동적으로 거래가 행해지는 상태를 나타내므로 참가자간에 네트웍 효과가 발생한다. 이를 구현하기 위해서는 어느 하나의 프로토콜로서는 용이하지 않으며 현재까지 ebXML, BizTalk, SOAP, RosettaNet, Eco Framewok, OPT 등의 프로토콜이 제시되어 표준화를 위한 노력을 해 오고 있다. 본 연구는 B2B Exchange를 구현하기 위해서 UDDI, SOAP, WSDL로 구성된 웹 서비스를 이용한 프레임을 설계하고 Apache 서버, SOAP 및 Xerces 환경에서 프로토타입을 구현하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.3 no.3
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• pp.183-188
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• 2002

Antibacterial glass ceramics composed of $5Li_2O{\cdot}36CaO{\cdot}20TiO_2{\cdot}27P_2O_5$ were Prepared. After ion exchange in the $AgNO_3$solution, crystallization phases were $AgTi_2(PO_4)_3$, $LiTi_2(PO_4)_3$ and $Ca_3(PO_4)_2$. In case of ion exchange, the crystallization phases started to be transformed from $LiTi_2(PO_4)_3$ to $AgTi_2(PO_4)_3$in 0.5 mole $AgNO_3$ solution and the transformation was almost completed in 1.0 mole. ion exchange rate of glass-ceramics powder, considering ion exchange time, was more fast than that of bulk. The bacteriostatic effect of the glass-ceramics on Staphyloroccus aureus and Salmonella typhi bacteria was more excellent than that of glass when the crystallization phase was transformed from LTP to AgTP.

• Journal of Distribution Science
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• v.10 no.7
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• pp.13-22
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• 2012

The effect of the September 2008 global financial crisis weighed heavily on stock markets around the world. The purpose of this study is to empirically investigate the impact of the crisis on Amman Stock Exchange. Event study methodology has been adopted on a period of 24 months, from January 2008 to December 2009. Monthly average abnormal returns across a sample of 52 industrial and services companies have been tested separately. The results reveal that Amman Stock Exchange experienced significant negative abnormal returns in the fourth quarter of the year 2008. However, there were no significant abnormal returns observed thereafter. This means that Amman Stock Exchange managed to overcome its adverse consequences. Since the event study tests for market efficiency, as well, the results show that Amman Stock Exchange reaction is consistent with the semi-strong form of the efficient market hypothesis.

• Fisheries and Aquatic Sciences
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• v.14 no.4
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• pp.421-428
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• 2011

We conducted modeling experiments to evaluate the residence times and exchange rates of seawater in Gamak Bay, located on the southern coast of the Korean Peninsula. The results revealed that pollutants are more quickly dispersed in a fixed grid rather than in a variable grid system. Pollutant concentrations decayed exponentially with time after release near the mouth of the bay, whereas no exponential variations were seen at the northwest end of the bay. The mean exchange rate of the seawater was 1.58% per day in the variable grid system, and the residence time of pollutants was greater than 288 days in Gamak Bay. Conversely, the exchange rate of seawater in Gamak Bay, as revealed by the particle tracking method, was 65% over a 50-day simulation. The results suggest that the seawater exchange in Gamak Bay is so low that pollutants are likely to remain in the bay indefinitely.