• The KIPS Transactions:PartB
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• v.9B no.5
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• pp.587-598
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• 2002

In multicast environment, the main objective of group key management is to provide security services to group communications by sharing a single group key among all the members of the group and subsequently encrypting and decrypting all the communication messages exchanged among the members of the group. Up to now, there has been no effort to develop group key management mechanism that considers the rate of users' join/leave operations. Hence, in this research, we propose group key management mechanisms that consider the rate of user's join/leave operations. We also define a new tree structure called variable tree which is much more flexible than full regular trees and show that variable trees are more efficient than full regular trees for group key management. Especially, we propose an algorithm that minimizes the necessary number of rekey messages according to the rate of join and leave operations. We also shows that if the rate of leave operation is greater than 50%, then the tree structure with degrees 2 or 3 are the optimal structures.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.6
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• pp.322-330
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• 2020

This study deals with underwater explosion (UNDEX) characteristics of various non-explosive underwater shock sources for the development of non-explosive underwater shock testing devices. UNDEX can neutralize ships' structure and the equipment onboard causing serious damage to combat and survivability. The shock proof performance of naval ships has been for a long time studied through simulations, but full-scale Live Fire Test and Evaluation (LFT&E) using real explosives have been limited due to the high risk and cost. For this reason, many researches have been tried to develop full scale ship shock tests without using actual explosives. In this study, experiments were conducted to find the characteristics of the underwater shock waves from actual explosive and non-explosive shock sources such as the airbag inflators and Vaporizing Foil Actuator (VFA). In order to derive the empirical equation for the maximum pressure value of the underwater shock wave generated by the non-explosive impact source, repeated experiments were conducted according to the number and distance. In addition, a Shock Response Spectrum (SRS) technique, which is a frequency-based function, was used to compare the response of floating bodies generated by underwater shock waves from each explosion source. In order to compare the magnitude of the underwater shock waves generated by each explosion source, Keel Shock Factor (KSF), which is a measure for estimating the amount of shock experienced by a naval ship from an underwater explosionan, was used.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.3
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• pp.49-56
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• 2022

ROK Navy intends to secure the Korean-type aircraft carrier in order to effectively prepare for various future security threats. In general, the Korean national competency is considered to be at the level of having an aircraft carrier, but it is unclear what scale aircraft carrier would be appropriate. In this study, the efficiency was evaluated through the relative comparison between national competency(national power, economic power) and the scale of aircraft carriers, and the optimal scale of the Korean-type aircraft carrier that could be acquired was presented. A DEA(Data Envelopment Analysis) model was applied to aircraft carriers(19 aircraft carriers in 11 countries) currently in operation and scheduled to be possessed in the world. As input variables, CINC(Composite Index of National Capability) and GDP(Gross Domestic Product), which are the most widely used as indicators of national and economic power, and as output variables, the full-load displacement, length, and width of aircraft carriers were selected. ARIMA(short-term within 5 years) and simple regression(long-term over 5 years) were used to estimate the future national competency of each country at the time of aircraft carriers acquisition. The relative efficiency score of the Korean-type aircraft carrier currently being evaluated is 1.062, and it was evaluated as small-scale aircraft carrier compared to the national competency. Based on Korean national competency, the optimal scale of the Korean-type aircraft carrier calculated by aggregating benchmark groups, is 58,308.1 tons of full-load displacement, 279.4m in length, and 68.3m in width.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.6
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• pp.1100-1105
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• 2017

In this paper, we propose a power control technique for D2D communication in the heterogenous network consisting of cellular and D2D communication systems. Although the transmit signal of D2D communication degrades the performance of cellular system by interfering the signal reception at CU in the conventional heterogenous networks without eavesdroppers, it can be utilized as jamming signal for preventing other devices from recovering the transmitted information if there are eavesdroppers in the network. The proposed power control technique maximizes the achievable rate of D2D communication while ensuring the target security performance of cellular communication system. Through simulation results, we validate the analysis results and compare the performance with the conventional D2D communication scheme that utilizes its full transmit power for maximizing the achievable rate regardless of the performance of cellular system.

• Journal of Digital Convergence
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• v.14 no.10
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• pp.295-302
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• 2016

Many countries, especially ICT powers, are supporting IoT-based technology at a national level and this technology is actively being researched in the businesses and research institutes in an aim to develop technology and create an ecosystem. Roads in the Seoul city are building public facilities based on IoT to provide various services and conveniences for the users. However, for the full-fledged introduction and development of IoT, there are many cases where infringement on security and privacy and threat for life and safety happen. Also, as the IoT environment includes various environment technologies such as the existing sensor network, heterogeneous communication network, and devices optimized for the IoT environment, it inherits the existing security threat and various attack techniques. This paper researches the attribute based encryption technology for safe communication in the IoT environment. The data collected from the device is transmitted utilizing the attribute based encryption and by designing the key generation protocol, grades and authorities for the device and users are identified to transmit safe messages.

• Journal of the Ergonomics Society of Korea
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• v.30 no.4
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• pp.551-562
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• 2011

Objective: We proposed an effective 3D menu manipulation alternative with a usability test. This was performed in a 3D environment with 3D menu and control manipulation methods. Background: As 3D stereoscopic displays became generalized, various 3D applications were being used not just movies, games, but also mobile contents and advertisements. However, when a user interface was designed in a 3D environment, it was lacked that a clear standard and result of an efficiency and usability as like a 2D environment. Method: We implemented 9 kinds of 3D menu types based on 3D menu hierarchies, menu layouts and dimensions. And we extracted 3 representative control types in a 3D environment. We performed usability evaluation with full factorial design for 27 menu alternatives with 2 types of menu manipulation tasks. In this condition, we measured the performance time, subjective discomfort and eye-fatigue. Results: A control type had the significant effect, and the effect of menu types had the different result depending on given tasks. Conclusion: This experiment showed the interaction of menu and control types depended on 3D menu manipulation tasks were significant in a 3D user interface design. Therefore, as a purpose of a 3D menu manipulation task, 3D menu types and control types were should be considered. Application: We supposed this result was should be applied in a 3D menu contents design.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.2
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• pp.501-522
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• 2016

In the digital era, information is a source of value creation. However, the growing importance of knowledge and information also increases risks and threats. When information is leaked, full recovery is difficult, and additional spreading of risk is high because it is easy to accomplish. Especially personal information is the main target due to its availability. Although individuals normally have to consent to the use of their personal information, they often do not know the use of their information. In such a difficult situation, one must exercise self-determination and privacy. Therefore, the goal of this study is to development a privacy literacy level measurement model for the proper exercise of the right to informational self-determination. It will be presented with the concept of privacy literacy index in order to determine the level of knowledge and understanding and practical application skills for individual. Through the index, we going to enhance the selection ability of information subject, and to promote the judgement and the determination capability for the protection and utilization of personal information.

• The KIPS Transactions:PartC
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• v.8C no.5
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• pp.525-534
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• 2001

Generally, compression and encryption procedures are performed independently in lossless image compression and encryption. When compression is followed by encryption, the compressed-stream should have the property of randomness because its entropy is decreased during the compression. However, when full data is compressed using image compression methods and then encrypted by encryption algorithms, real-time processing is unrealistic due to the time delay involved. In this paper, we propose to combine compression and encryption to reduce the overall processing time. It is method decomposing gray-scale image by means of quadtree compression algorithms and encrypting the structural part. Moreover, the lossless compression ratio can be increased using a transform that provides an decorrelated image and homogeneous region, and the encryption security can be improved using a reconstruction of the unencrypted quadtree data at each level. We confirmed the increased compression ratio, improved encryption security, and real-time processing by using computer simulations.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.58
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• pp.179-213
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• 2013

While a performance type guarantee is required as a security for non-performance risk by a seller, a payment guarantee is used as a security for non-payment risk by a buyer(or a borrower in a loan agreement). A payment guarantee is a type of independent bank guarantee, bank guarantee, bond, demand guarantee, or standby letter of credit. A guarantor accepts a credit risk of a principal which is normally a buyer in a contract for sale of goods. A payment guarantee is independent of the underlying relationship between the applicant and the beneficiary. The guarantor is only empowered to examine the beneficiary's demand and determine the payment on its face to the terms of the guarantee. A payment guarantee is thus different from a suretyship. The principle of independence carries a significant advantages for a guarantor as well as for a beneficiary. While a documentary credit requires B/L, commercial invoice, packing list, inspection certificate, etc., a typical payment guarantee does not require any evidence for a seller's performance of the underlying contract other than written demand. In this respect payment guarnatee can be a more secured facility than a documentary credit. A payment guarantee normally comes into force from the issuing date and shall remain in effect until all sums guaranteed shall be paid in full by a buyer(or a borrower) or by a guarantor. Although a guarantor shall pay a demand made in accordance with the terms and conditions of the payment guarantee, a payment demand may be denied when it is determined to be abusive or unfair.

• Convergence Security Journal
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• v.9 no.2
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• pp.79-84
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• 2009

Recently, Move Picture Files have the same file format and a compression technique as Window Media Video form. but Moving Pictures using file format and a compression technique have question about Motion blur and compressibility. In this paper, we design and Implement for new Move Picture Solution EZ-MOV using FLV different from developed FLV(Flash Video) in the Macromedia company. EZ-MOV have advantages as follow. first, FLV player is able to compact disk access time and DRM (Digital Rights Management) with a built-in self and unable to an illegal video recording, second, whenever WMV formal file encoded FLV are able to lossless compression to fifty percent, third, FLV is able to Moving Picture streaming no buffering. fourth, FLV file is able streaming service no streaming server. fifth, FLV file is able to streaming service keep pace with download and streaming. sixth, FLV file is able to full duplex service.