• Knowledge Management Research
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• v.14 no.3
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• pp.55-85
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• 2013

The present study examines the effects of transformational leadership exercised by team leader and transformational leadership shared by team members on team creativity and team performance at the team level. A growing body on leadership research highlights the role of team leadership in work organizations. In team settings, studies have focused exclusively on individual leaders who occupy formal leadership positions and exercise vertical influence over team members. In contrast to this traditional approach, shared leadership highlights a horizontal influence process where leadership is collectively carried out by team members. In this shared form of leadership, members actively participate in the leadership process and horizontally influence other team members. This mutual influence among team members constitutes a critical condition for the success of team-based organizations. The ability of team members to work together as a team is the key to the overall functioning of the team organization. To verify the effect of two leadership styles, we analyze the effect of a leader's transformational leadership and members' shared transformational leadership on team creativity and team performance for the same team. This study also predicts that the transformational leadership shared by members will moderate the effects of leader transformational leadership on team performance and creativity. Our findings show that both leaderships have a positive effect on team performance. However, the main effect of a leader's transformational leadership on team creativity is not significant when members' transformational leadership is employed into the model. With the effect of leader transformational leadership controlled for, the main effects of the transformational leadership shared by members on team creativity and performance are significant. In addition, we also found the significant moderation effects of member transformational leadership by leader transformational leadership on team creativity. Based on these findings, we strongly recommend that team based organizations shift the leadership focus from the leader focused leadership model to the shared leadership model. We also discuss managerial implications of our findings in details.

• Convergence Security Journal
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• v.15 no.7
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• pp.103-110
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• 2015

The security of the data exchanged between sensor nodes in IoT (Internet of Things) environment becomes increasing. In the conventional IEEE 802.15.4, the key for secure communication between the sensor node and the sensor node and the PAN Coordinator or the sensor node is assumed to be pre-shared in advance. Especially, there is another problem in that sensor node authentication is not considered during the association process. In this paper, we propose a security scheme that solves the problems of previously proposed protocols with the pre-shared key for all devices.

• Journal of the Korean housing association
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• v.25 no.6
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• pp.123-132
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• 2014

Proportion of senior population living alone in South Korea has exceeded over 20.2% in 2012, and it is anticipated that the proportion would increase every year. Poverty rate of seniors living alone in Korea is also anticipated to increase the highest rate (76.6%) among OECD countries. In particular, seniors lacking family support are having greater difficulty and isolated due to high housing costs and housing instability. Therefore, they need a new housing alternatives for considering their economical difficulty and lacking family and social support. This study attempted to examine possibility to develop a new housing alternatives for Korean seniors, especially living urban area. For this purpose, this study identified the attitudes and preference for a new house alternatives(Senior Shared House) by Korean seniors living alone. The key findings of this study were as follows: 1) Eighty-five percent of seniors participated in this study responded the senior shared house was needed. 2) It should be developed by utilizing or renovating and renting out existing housing in city areas. 3) Pre-residence checklist can be developed to connect and match prospect residents. 4) Professional workforce (e.g. housing welfare professional) is absolutely necessary to perform the role of coordinator understanding the various characteristics of the seniors, and their living requirements. Recommendations and directions for future development of senior shared house were suggested.

• Journal of Power Electronics
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• v.16 no.2
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• pp.805-814
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• 2016

Electric-field coupled power transfer (ECPT) systems have been proposed as an alternative wireless power transfer (WPT) technology in recent years. With the use of capacitive plates as a coupling structure, ECPT systems have many advantages such as design flexibility, reduced volume of the coupling structure and metal penetration ability. In addition, wireless communications are effective solutions to improve the safety and controllability of ECPT systems. This paper proposes a power and signal shared channel for electric-field coupled power transfer systems. The shared channel includes two similar electrical circuits with a band pass filter and a signal detection resistor in each. This is designed based on the traditional current-fed push-pull topology. An analysis of the mutual interference between the power and signal transmission, the channel power and signal attenuations, and the dynamic characteristic of the signal channel are conducted to determine the values for the electrical components of the proposed shared channel. Experimental results show that the designed channel can transfer over 100W of output power and data with a data rate from 300bps to 120 kbps.

• The Transactions of the Korea Information Processing Society
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• v.4 no.11
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• pp.2690-2700
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• 1997

This paper presents parallel sorting algorithm, SHARED-MEMORY-BS and REDUCED-BS, which are implemented on shared-memory parallel computers. These algorithm sort N keys in $O(log^2N)$ time. REDUCED-BS users a parity strategy which gives an idea for the efficient usage of the local memory associated with each processor. By taking advantage of the local memory associated with each processor, the communication of REDUCED-BS is decreased by approximately half that of SHARED-MEMORY-BS. On the basis of alleviating the communication, the algorithm REDUCED-BS results in a significant improvement of performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.10
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• pp.3557-3571
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• 2014

We develop a secret key generation scheme using phase estimation in ultra-wideband (UWB) wireless fading channels. Based on the reciprocity theorem, two terminals extract the phase of the channel as a common random source to generate secret bits. Moreover, we study the secret key rate by a pair of nodes observing correlated sources and communicating to achieve secret key agreement over public communication channels. As our main results, we establish a more practical upper bound from Cramer-Rao bound (CRB) and compare it with a universally theoretical upper bound on the shared maximum key rate from mutual information of correlated random sources. Derivation and numerical examples are presented to demonstrate the bound. Simulation studies are also provided to validate feasibility and efficiency of the proposed scheme.

• Journal of Korea Multimedia Society
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• v.9 no.12
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• pp.1649-1656
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• 2006

Renewal of the group key on the mobile communication needs it can be not re-shared by all members of the group with the exception of excluded members but also prevented from making a fraudulent use of group key due to leakage of security information for terminal. In this paper, we propose an efficient renewal mechanism of group key in order for all members of the group to be able to get digital information and to perform the renewal of group key employing the Fiat-Shamir method. It can guarantee the security of a group key since a terminal renews a group key by using security information of an excluded terminal and the previous group key.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.6
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• pp.1343-1354
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• 2018

OAuth 2.0 bearer token and JWT(JSON web token), current standard technologies for authentication and authorization, use the approach of sending fixed token repeatedly to server for authentication that they are subject to eavesdropping attack, thus they should be used in secure communication environment such as HTTPS. In OAuth 2.0 MAC token which was devised as an authentication scheme that can be used in non-secure communication environment, server issues shared secret key to authenticated client and the client uses it to compute MAC to prove the authenticity of request, but in this case server has to store and use the shared secret key to verify user's request. Therefore, it's hard to provide stateless authentication service. In this paper we present a randomized token authentication scheme which can provide stateless MAC token authentication without storing shared secret key in server side. To remove the use of HTTPS, we utilize secure communication using server certificate and simple signature-based login using client certificate together with the proposed randomized token authentication to achieve the fully stateless authentication service and we provide an implementation example.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.5
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• pp.771-780
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• 2020

QKD(Quantum Key Distribution) is one of the protocols that can make two distant parties safely share secure keys against the threat of quantum computer. Generally, cryptographic applications which are connected to the QKD device have fixed roles as a transmitter and a receiver due to the race condition and complexity of implementation. Because the conventional QKD system is mainly applied to the link encryptor, there are no problems even if the roles of the cryptographic devices are fixed. We propose a new scheme of QKD system and protocol that is easy to extend to the QKD network by eliminating quantum key dependency between cryptographic device and QKD node. The secure keys which are generated by the TRNG(True Random Number Generator) are provided to the cryptographic applications instead of quantum keys. We design an architecture to transmit safely the secure keys using the inbound and outbound quantum keys which are shared between two nodes. In this scheme, since the dependency of shared quantum keys between two QKD nodes is eliminated, all cryptographic applicatons can be a master or a slave depending on who initiates the cryptographic communications.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.4
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• pp.822-839
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• 2011

Group key agreement protocols derive a shared secret key for a group of users to ensure data confidentiality or/and integrity among the users in the subsequent communications. In this paper, we inspect two group key agreement schemes which have been proposed by Shi et al. and Zheng et al. in 2005 and 2007 respectively. Although both schemes were claimed to be secure in a heuristic way, we reveal several flaws using the Bellare-Rogaway security model extended to multi-party setting by Bresson et al. These flaws are found to be originated from inappropriate selection of key derivation function, inadvertent exclusion of partners' identities from the protocol specification and insufficient consideration in preserving known temporary information security and key freshness properties. Furthermore, we suggest and discuss proper countermeasures to address such flaws.