• ETRI Journal
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• v.38 no.5
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• pp.934-940
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• 2016

In this paper, secure multicasting with the help of cooperative decode-and-forward relays is considered for the case in which a source securely sends a common message to multiple destinations in the presence of a single eavesdropper. We show that the secrecy rate maximization problem in the secure multicasting scenario under an overall power constraint can be solved using semidefinite programing with semidefinite relaxation and a bisection technique. Further, a suboptimal approach using zero-forcing beamforming and linear programming based power allocation is also proposed. Numerical results illustrate the secrecy rates achieved by the proposed schemes under secure multicasting scenarios.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.10
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• pp.5049-5062
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• 2016

This paper analyzes the secrecy performance of an amplify-and-forward (AF) relay network, where a multi-antenna eavesdropper attempts to overhear the transmitted message from a multi-antenna source to a multi-antenna destination with a single antenna relay. Firstly, we derive the approximate analytical expressions for the secrecy outage probability (SOP) and average secrecy rate (ASR) of the relay network. Then, asymptotic expressions of SOP and ASR at high main-to-eavesdropper ratio (MER) are also provided to reveal the diversity gain of the secure communication. Finally, numerical results are given to verify the theoretical analysis and show the effect of the number of antennas in the considered relay network.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.2
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• pp.107-114
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• 1999

This paper presents an application of artificial neural networks(ANN) to assess the dynamic security of power systems. The basic role of ANN is to provide assessment of the system's stability based on training samples from off-line analysi. The critical clearing time(CCT) is an attribute which provides significant information about the quality of the post-fault system behaviour. The function of ANN is a mapping of the pre-fault, fault-on, and post-fault system conditions into the CCT's. In previous work, a feed forward neural network is used to learn this mapping by using the generation outputs during the fault as the input data. However, it takes significant calculation time to make the input data through the network reduction at a fault as the input data. However, it takes significant calculation time to make the input data through the network reduction at a fault considered. In order to enhance the speed of security assessment, the bus data and line powers are used as the input data of the ANN in thil paper. Test results show that the proposed neural networks have the reasonable accuracy and can be used in on-line security assenssment efficiently.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.12
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• pp.2695-2701
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• 2012

We need privacy protection protocols, that satisfy three essential security requirements; confidentiality, indistinguishability and forward security, in order to protect user's privacy in RFID system. The hash-chain based protocol that Ohkubo et. al proposed is the most secure protocol, that satisfies all of the essential security requirements, among existing protocols. But, this protocol has a disadvantage that it takes very long time to identify a tag in the back-end server. In this paper, we propose a scheme to keep security just as it is and to reduce computation time for identifying a tag in back-end server. The proposed scheme shows the results that the identification time in back-end server is reduced considerably compared to the hash-chain based protocol.

• Annual Conference of KIPS
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• 2002.11b
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• pp.841-844
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• 2002

이 논문에서는 동적이고 규모가 큰 그룹에 대해서 한명의 그룹 관리자가 존재하면서, 특별히 새로운 그룹키가 갱신될 때마다 새로운 정보를 받기 힘든 구성원, 즉 스테이트리스 리시버(stateless receiver)에게 적합한 방법을 제안한다. 이 방법은 구성원에게 각각 한 개씩 주어지는 개인키를 전송하는 메시지를 제외한 다른 모든 메시지들에는 암호화 과정이 요구되지 않는다. 즉, 갱신된 그룹키를 공유하기 위해 필요한 계산은 단지 O($log_2$n) 번의 해쉬함수 계산과 배타적 논리합(XOR)을 수행하는 것이며, 그룹키를 갱신하기 위해 필요한 정보는 암호화될 필요없는 멀티캐스트 메시지와 그룹에 추가될 때 그룹 관리자로부터 받은 초기값이다. 또한 제안하는 방법은 새롭게 추가된 사람이 이전의 그룹키에 대한 어떠한 정보도 알 수 없으며(후방보호 : Backward Secrecy), 삭제되는 사람 역시 이후의 새로운 그룹키에 대한 정보를 알 수 없다(전방보호 : Forward Secrecy). 또한 제안된 방법에 게시판이 이용된다면, 각 그룹의 구성원은 어떠한 멀티캐스트 메시지없이 단지 자신의 초기 개인키만으로 필요한 모든 노드키들을 계산할 수 있다.

• Convergence Security Journal
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• v.15 no.5
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• pp.37-45
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• 2015

In IT system, logs are an indicator of the previous key events. Therefore, when a security problem occurs in the system, logs are used to find evidence and solution to the problem. So, it is important to ensure the integrity of the stored logs. Existing schemes have been proposed to detect tampering of the stored logs after the key has been exp osed. Existing schemes are designed separately in terms of log transmission and storage. We propose a new log sys tem for integrating log transmission with storage. In addition, we prove the security requirements of the proposed sc heme and computational efficiency with existing schemes.

• Journal of Power Electronics
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• v.15 no.1
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• pp.86-95
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• 2015

An active clamp high step-up boost converter with a coupled inductor is proposed in this paper. In the proposed strategy, a coupled inductor is adopted to achieve a high voltage gain. The clamp circuit is included to achieve the zero-voltage-switching (ZVS) condition for both the main and clamp switches. A rectifier composed of a capacitor and a diode is added to reduce the voltage stress of the output rectifier diode. As a result, diodes with a low reverse-recovery time and forward voltage-drop can be utilized. Since the voltage stresses of the main and clamp switches are far below the output voltage, low-voltage-rated MOSFETs can be adopted to reduce conduction losses. Moreover, the reverse-recovery losses of the diodes are reduced due to the inherent leakage inductance of the coupled inductor. Therefore, high efficiency can be expected. Firstly, the derivation of the proposed converter is given and the operation analysis is described. Then, a steady-state performance analysis of the proposed converter is analyzed in detail. Finally, a 250 W prototype is built to verify the analysis. The measured maximum efficiency of the prototype is 95%.

• The KIPS Transactions:PartC
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• v.9C no.6
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• pp.799-808
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• 2002

According to the wide-spread of information transmission system over network, the use of cryptographic system to provide the integrity of transmitted message over network is increasing and the importance of that is emphasized. Because the security of the cryptographic system totally relies on the key, key management is a essential part of cryptographic system. A number of key agreement protocols have been proposed to far, but their rigorous security analysis is still open. In this paper, we analyze the features of Diffie-Hellman based standard key agreement protocols and provide the security analysis of those protocols against several kinds of active attacks.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.6
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• pp.1022-1025
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• 2008

Session Initiation Protocol (SIP) has become the call control protocol of choice for Voice over IP (VoIP) networks because of its open and extensible nature. However, the integrity of call signaling between sites is of utmost importance, and SIP is vulnerable to attackers when left unprotected. Currently a herby-hop security model is prevalent, wherein intermediaries forward a request towards the destination user agent sewer (UAS) without a user agent client (UAC) knowing whether or not the intermediary behaved in a trusted manner. This paper presents an integrated security model for SIP-based VoIP network by combining hop-by-hop security and end-to-end security.

• Korean Security Journal
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• no.15
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• pp.173-198
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• 2008

As we took a look at above, this researcher suggest following device to extend Korea's private security industry's area. First, it is necessary to extend private investigation law's area grafting private security together. Second, it is necessary it is necessary to think of private security's role related key figure law, corresponding terror law, Presidential Security Service Guard law. Third, as a draft of a proposed law related prevention flowing out of industry techniques among industry security related law, passed, it is necessary private security's diversity, subdivision, composition through an enterprise security, and private security industry area's grafting together. Fourth, a research about private security company's investment and professional area's bringing up as well as business's extension device should be groped for the security consulting though total system management service. Fifth, there are no big difference education course and purpose, duty about a security police man law and security law's unification, so it is necessary to drive forward actively unification through government organization's cooperation. Sixth, a paradigm shift should be occured about private security service among policeman, citizen, and private security guards. Seventh, it is considered the role of security association is important. Lastly about a matter communication between the National Police Agency, and Security Association, not only look at from an authority's angle, collecting information, corresponding ability but now it is considered to grope each other cooperation device together among organizations not only the National Police Agency but also, National Organization, National Intelligence Service, the prosecution, Presidential Security Service Guard, Army etc.