• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.4
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• pp.605-610
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• 2013

A cryptography for enforcing hierarchic groups in a system where hierarchy is represented by a partially ordered set was introduced by Akl et al. But the key generation algorithm of Akl et al. is infeasible when there is a large number of users. To overcome this shortage, in 1985, MacKinnon et al. proposed a paper containing a condition which prevents cooperative attacks and optimizes the assignment. In 2005, Kim et al. proposed the key management systems for using one-way hash function, RSA algorithm, poset dimension and Clifford semigroup in the context of modern cryptography, the key management system using Clifford semigroup of imaginary quadratic non-maximal orders. We, in this paper, show that Kim et al. cryptosystem is insecure in some reasons and propose a revised cryptosystem.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.6
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• pp.1561-1569
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• 2016

As the use of the sensor device increases in IoT environment, the need for device security is becoming more and more important When a sensor device is deployed in IEEE 802.15.4-based LoWPAN, it has to perform the join operation with PAN Coordinator and the binding operation with another device. In the join and binding process, authentication and key distribution of the device are performed using the pre-distributed network key or certificate. However, the network key used in the conventional method has problems that it's role is limited to the group authentication and individual identification is not applied in certificate issuing. In this paper, we propose a secure join and binding protocol in LoWPAN environment that solves the problems of pre-distributed network key.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.500-502
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• 1998

m-to-m 그룹 통신망의 보안은 기본의 m-to-1통신에서는 고려되지 않았던 보안 문제가 발생한다. 이중에서도 통신데이터정보의 비밀을 보장하기 위한 암호화에 사용되어지는 키교환을 어떻게 할 것 인가에 대하여 해결해야 한다. m-to-m 통신상의데이터 암호화는 통신에 참여하는 모든 멤버가 동일한 키를 가져야 한다. 따라서 본 논문에서는 Diffie-Hellman 알고리즘을 이용한 그룹상의 키교환 방식을 살펴본 후 효율성면에서 개선한 그룹키교환 방식을 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.757-759
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• 2002

본 논문에서는 ID 보안 기술에 기반을 둔 디지털서명, 키분배 기법을 이용하여 그룹 비밀키의 분배와 갱신을 위한 효율적인 프로토콜을 제안한다. 제안된 프로토콜의 안전성은 이산대수 문제에 근거하고 있으며 단말기의 저장능력과 처리의 능력이 적을 경우도 적절하게 운영될 수 있고, 그룹 내에서 제외하고자하는 통화자가 동시에 여러 명일 경우에도 적용한 수 있다. 또한 통화자의 변동 없이 그룹 비밀키를 변경하고자 하는 경우에도 용이하게 키를 갱신할 수 있도록 설계되었다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10a
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• pp.748-750
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• 2001

최근 인터넷을 통한 네트워크 응용들의 확산은 unicast에서 multicast로 넓혀가고 있는 추세이다. 그러나 공개키 쌍을 사용하는 PKI 키 관리 및 인증기법에 반해 그룹 키 관리 및 인증기법에 대한 연구는 아직 미비한 상태이다. 따라서 본 논문에서는 동일한 보안등급을 갖는 다중 사용자들이 보다 안전하게 키를 공유하고 인증할 수 있도록 하는 그룹 키 분산 기법에서, 즉, 그룹키를 관리함에 있어서 필요한 정보보호에 대한 고찰 및 그룹 키 관리에서의 주요 처리인 join/leave 함수 처리, 다양한 그룹키 분산 기법에 관하여 연구하고 보다 안전한 키 관리 및 객체가 갖는 장점들을 포함하는 안전한 그룹 키 분산기법에 관하여 논하도록 한다.

• Journal of the Korea Convergence Society
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• v.8 no.12
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• pp.9-14
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• 2017

Recently, the Internet of Things are developing in accordance with the technology of implementation in low-cost, small-size, low power consumption and smart sensor that can communicate using the internet. Especially, key management researches for secure information transmission based on the Internet of Things (IoT) are actively performing. But, Internet of Things(IoT) are uses sensor. Therefore low-power consumption and small-memory are restrictive condition. As a result, managing the key is difficult as a general security measure. However, The problem of secure key management is an essential challenge For the continuous development of the Internet of things. In this paper, we propose a key distribution and management technique in secure Internet of things. In the key generation and management stage, it satisfies the conditions and without physically constrained for IoT based communication.

• Journal of KIISE:Information Networking
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• v.31 no.4
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• pp.353-362
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• 2004

Mobile Ad-Hoc network tends to expose scarce computing resources and various security threats because all traffics are carried in air along with no central management authority. To provide secure communication and save communication overhead, a scheme is inevitable to serurely establish session keys. However, most of key establishment methods for Ad-Hoc network focus on the distribution of a group key to all hosts and/or the efficient public key management. In this paper, a secure and efficient scheme is proposed to establish a session key between two Ad-Hoc nodes. The proposed scheme makes use of the secret sharing mechanism and the Diffie-Hellman key exchange method. For secure intra-cluster communication, each member node establishes session keys with its clusterhead, after mutual authentication using the secret shares. For inter-cluster communication, each node establishes session keys with its correspondent node using the public key and Diffie-Hellman key exchange method. The simulation results prove that the proposed scheme is more secure and efficient than that of the Clusterhead Authentication Based Method(1).

• Journal of Distribution Science
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• v.16 no.12
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• pp.47-56
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• 2018

Purpose - The potential use of cryptocurrencies in a retail environment proposes a rapid shift from the traditional financial system. Nakamoto(2008) defines Bitcoin as an open source alt-coin based on the blockchain technology. Luther(2016) insists that the new technology will be widely adopted for the digital payment processes. However, the use of Bitcoin is in the real world is still sparse. Despite the growing attention and purported benefits, it is doubtful whether the Bitcoin will be eagerly accepted by ordinary consumers in the mainstream market. To answer this question, this paper develops a causal model that has a dual path to explain the motivation to adopt Bitcoin. According to Glaser, Zimmermann, Haferkorn, Weber, and Siering(2014), Bitcoin is both an asset and a currency at the same time. In summary, the attitude towards Bitcoin may vary depending on whether the fin-tech product is viewed as an asset or as a currency. Based on the arguments, we propose that asset attitude and currency attitude will give influence to consumers' intention to adopt Bitcoin. Research design, data, and methodology - Quantitative data collection is conducted from a Bitcoin SIG(special interest group) working in an internet community. As a result, 192 respondents who know Bitcoin completed the survey. To analyze the causal relations in the research model, PLS-SEM(partial least squares structural equation modeling) method is used. Also, reliability and validity of measures are tested by performing Cronbach's alpha test, Fornell-Larcker test and confirmatory factor test. Results - Our test results show that every hypothesis is supported except the influence of perceived ease of use. In addition, we find that the relationships between constructs are different between the high innovative group and low innovative group. Conclusions - We provide evidence that asset attitude and currency attitude are key antecedents of Bitcoin adoption.

• Journal of Power Electronics
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• v.19 no.1
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• pp.234-243
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• 2019

Studying the control strategy of a microgrid under the load unbalanced state helps to improve the stability of the system. The magnitude of the power fluctuation, which occurs between the power supply and the load, is generated in a microgrid under the load unbalanced state is called negative sequence reactive power $Q^-$. Traditional power distribution methods such as P-f, Q-E droop control can only distribute power with positive sequence current information. However, they have no effect on $Q^-$ with negative sequence current information. In this paper, a stationary-frame control method for power sharing and voltage unbalance compensation in islanded microgrids is proposed. This method is based on the proper output impedance control of distributed generation unit (DG unit) interface converters. The control system of a DG unit mainly consists of an active-power-frequency and reactive-power-voltage droop controller, an output impedance controller, and voltage and current controllers. The proposed method allows for the sharing of imbalance current among the DG unit and it can compensate voltage unbalance at the same time. The design approach of the control system is discussed in detail. Simulation and experimental results are presented. These results demonstrate that the proposed method is effective in the compensation of voltage unbalance and the power distribution.

• Journal of Genetic Medicine
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• v.1 no.1
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• pp.17-22
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• 1997

The angiotensin converting enzyme (ACE) is a key component of the renin-angiotensin system thought to be important in the pathogenesis of hypertension and cardiovascular diseases. Deletion polymorphism in the ACE gene may be a risk factor for myocardial infarction. The insertion/deletion (I/D) polymorphism of the ACE detected by PCR analysis appears to be associated with hypertension in Koreans and its nucleotide was subcloned into T-vector and its nucleotide sequences were determined. We also examined an association between hypertension and genetic variance of ACE. We identified the angiotensin I-converting enzyme genotype in 127 hypertensive and 189 normotensive Korean subjects. The distribution of ACE genotype II, ID, DD were 39.2%, 40.2%, 20.6% respectively and the frequency for ACE alleles I and D were 0.593 and 0.407, respectively in all subjects. The frequency of D allele in Korean males is higher than that of Korean females (male; 0.438 : female; 0.267), and the frequency of I allele in Korean females is higher than that of Korean males (female; 0.733 : male; 0.562). Genotype distributions of angiotensin I-converting enzyme genes in Korean normal adult population were different from that of Caucasians (P<0.001). There were no significant differences in genotype frequency between the hypertensive control group (n=127) and the normotensive group (n=189). We observed significant differences of ACE genotype distribution between the male group and the female group in total (P=0.001) and in hypertensive Korean subjects (P=0.013).