• Journal of Communications and Networks
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• v.14 no.6
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• pp.682-691
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• 2012

Key agreement protocol is a fundamental protocol in cryptography whereby two or more participants can agree on a common conference key in order to communicate securely among themselves. In this situation, the participants can securely send and receive messages with each other. An adversary not having access to the conference key will not be able to decrypt the messages. In this paper, we propose a novel identity-based authenticated multi user key agreement protocol employing a symmetric balanced incomplete block design. Our protocol is built on elliptic curve cryptography and takes advantage of a kind of bilinear map called Weil pairing. The protocol presented can provide an identification (ID)-based authentication service and resist different key attacks. Furthermore, our protocol is efficient and needs only two rounds for generating a common conference key. It is worth noting that the communication cost for generating a conference key in our protocol is only O($\sqrt{n}$) and the computation cost is only O($nm^2$), where $n$ implies the number of participants and m denotes the extension degree of the finite field $F_{p^m}$. In addition, in order to resist the different key attack from malicious participants, our protocol can be further extended to provide the fault tolerant property.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.556-558
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• 2005

SLA(Service Level Agreement)는 최근 들어 IT서비스를 받는 고객들에게 서비스 보장에 대한 명확한 계약과 일정수준 이상의 서비스 관리 제공으로 의무화 추세가 증가되고 있다. 또한 서비스 공급자는 변화하는 고객의 요구사항을 직면하여 SLA의 적용을 통해 서비스 Quality를 높이는데 주력하고 있다. 특히 특정 가입자가 두지점 사이에 교환 설비를 거치지 않고 직접 연결하여 독점적으로 사용할 수 있는 전용회선 서비스는 End-To-End간의 품질보증을 기본 목적으로 하고는 있지만 저렴한 요금의 프레임릴레이 ATM, VPN등 대체서비스로의 이동이 이어지고 있어 고객 측면의 새로운 방안 제시가 필요한 실정이다.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.906-909
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• 2015

ITSM(IT Service Management)은 2000년대 중반 이후 기업 및 공공기관에 본격적으로 적용되기 시작하였다. ITSM의 한 부분으로 IT 조직에서는 외주업체와 SLA(Service Level Agreement)을 체결하여 정보시스템 서비스의 품질을 적정수준으로 관리토록 노력하고 있다. 그러나 SAL를 적용하는 서비스 측정항목을 선택하는데 있어 측정이 비교적 용이한 서버 운영시간, 서버 성능, 서비스 가동률 등 서버운영에 주로 초점이 맞춰져 왔다. 응용시스템에 대한 서비스 요청 적기 처리율, 변경요청 적기 처리율 등에 대해서는 고객과 외주업체의 협의요소 증가, 데이터 관리 및 정확성 부족 등으로 SLA 항목에서 제외되어 왔다. 본 논문에서는 응용시스템의 유지보수 관련 SLA 적용에 초점을 맞춰 서비스데스크 구축방안을 제시하였다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2007.04a
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• pp.225-229
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• 2007

We propose some properties of fuzzy p-value and fuzzy significance level to the fuzzy hypotheses testing for vague response data with reflected correlation in survey research, Appling the principle of agreement index, we suggest the methods for fuzzy hypothesis testing by fuzzy rejection region.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.12
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• pp.4950-4966
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• 2015

Cloud providers now face the problem of estimating the amount of computing resources required to satisfy a future workload. In this paper, a virtual machine provisioning (VMP) mechanism is designed to adapt workload fluctuation. The arrival rate of forthcoming jobs is predicted for acquiring the proper service rate by adopting an exponential smoothing (ES) method. The proper service rate is estimated to guarantee the service level agreement (SLA) constraints by using a diffusion approximation statistical model. The VMP problem is formulated as a facility location problem. Furthermore, it is characterized as the maximization of submodular function subject to the matroid constraints. A greedy-based VMP algorithm is designed to obtain the optimal virtual machine provision pattern. Simulation results illustrate that the proposed mechanism could increase the average profit efficiently without incurring significant quality of service (QoS) violations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.7
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• pp.3371-3396
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• 2016

Authentication protocols for multi-server architectures have gained momentum in recent times due to advancements in computing technologies and associated constraints. Lu et al. recently proposed a biometrics and smartcards-based authentication scheme for multi-server environment. The careful analysis of this paper demonstrates Lu et al.'s protocol is susceptible to user impersonation attacks and comprises insufficient data. In addition, this paper proposes an improved authentication with key-agreement protocol for multi-server architecture based on biometrics and smartcards. The formal security of the proposed protocol is verified using the widely accepted AVISPA (Automated Validation of Internet Security Protocols and Applications) tool to ensure that our protocol can withstand active and passive attacks. The formal and informal security analysis, and performance analysis sections determines that our protocol is robust and efficient compared to Lu et al.'s protocol and existing similar protocols.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.12
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• pp.5572-5595
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• 2016

Multi-server authentication enables the subscribers to enjoy an assortment of services from various service providers based on a single registration from any registration centre. Previously, a subscriber had to register from each service provider individually to avail respective services relying on single server authentication. In the past, a number of multi-server authentication techniques can be witnessed that employed lightweight and even computationally intensive cryptographic operations. In line with this, Zhu has presented a chaotic map based multi-server authentication scheme recently, which is not only vulnerable to denial-of-service attack, stolen-verifier attack, but also lacks anonymity. This research aims at improving the Zhu's protocol in terms of cost and efficiency. Moreover, the comparative study is presented for the performance of improved model against the existing scheme, and the security of proposed model is formally proved using BAN Logic.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.2
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• pp.188-198
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• 2012

An improvement to the k-${\varepsilon}$ turbulence model is presented and is shown to lead to better agreement with data regarding supersonic base flows. The improvement was achieved by imposing a grid-independent realizability constraint in the Launder-Sharma k-${\varepsilon}$ model. The effects of compressibility were also examined. The numerical results show that the modified Launder-Sharma model leads to some improvement in the prediction of the velocity and turbulent kinetic energy profiles. Compressibility corrections also lead to better agreement in both the turbulent kinetic energy and the Reynolds stress profiles with the experimental data.

• Journal of Power System Engineering
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• v.18 no.1
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• pp.135-139
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• 2014

We propose some properties for fuzzy hypothesis test by fuzzy significance probability. First, we define fuzzy number data and fuzzy significance probability for repeatedly observed data with alternated error term. By the agreement index, we compare fuzzy significance probability with significance level and drawing conclusions the degree of acceptance and rejection by agreement index.

• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.95-99
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• 1999

We proposed a new retrieval method for aerosol's real part of refractive index, optical thickness, and Angstrom exponent using POLDER's directional reflectance and polarization data. We showed that aerosol's real part of refractive index can be retrieved systematically using multi-directional PR(polarization and reflectance) diagrams in a single infrared band by our algorithm for the first time. We examined the retrieved results, by comparing with the simultaneously measured sky observation data at the study site and we obtained a reasonable agreement between them.