• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.3
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• pp.547-557
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• 2015

The security of all cryptographic algorithms and protocols is based on the confidentiality of secret keys. Key management mechanism is an indispensable part of the cryptographic system and this deals with the generation, exchange, storage, use, and replacement of keys. Within the key management mechanism there are key derivation functions (KDFs) which derive one or more keys from a master key. NIST specifies three families of PRF-based KDFs in SP 800-108. In this paper, we examine the difference of security models between the KDFs and the encryption modes of operations. Moreover we focus on the provable security of PRF-based KDFs according to input types of counters, and show that the counter and feedback modes of KDFs using XOR of counters are insecure, while these modes using concatenation of counters are secure.

• Journal of Digital Convergence
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• v.15 no.3
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• pp.87-98
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• 2017

As the market for coffee chains becomes fierce, it is important for coffee chains to establish an enduring relationship with customers and encourage them to revisit their stores. Thus, it becomes important to understand consumers' repurchase decision-making mechanisms in the context of coffee chains. Customer satisfaction, perceived switching costs, and regret were considered as the main factors of customers' repurchase intentions. Especially, the effect of regret experience of coffee chains on consumers' repurchase decision was examined. In addition, coffee quality, physical environment quality, service encounters performance, and brand trust were considered as attributes of coffee shop selection, and their effects on customer satisfaction and perceived switching cost were investigated. The results of the study showed that customer satisfaction and perceived switching costs had a positive effect on repurchase intention, while regret had a negative effect on repurchase intention. Coffee quality and physical environmental quality had no significant effect on customer satisfaction and perceived conversion cost. Service encounter performance had a significant impact on perceived switching costs alone. Brand trust had a significant impact on both customer satisfaction and perceived switching cost.

• Journal of IKEEE
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• v.16 no.4
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• pp.322-327
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• 2012

In this paper, a digital phase-locked loop(Digital-PLL) circuit with a new phase-to-digital converter(P2D) is described. The proposed digital PLL is composed a P2D, a digital loop filter(DLF), and a digitally controlled oscillator(DCO). The P2D generates a digital code for a phase error. The proposed P2D used a binary phase frequency detector(BPFD) and a counter in place of a time-to-digital converter(TDC) for simple structure, compact area and low power consumption. The proposed circuit was designed with CMOS 0.18um process. The simulation shows the circuit operates with the 1.0 to 2.2GHz with the power consumption of 16.2mW at 1.65GHz and the circuit occupies the chip area of $0.096mm^2$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6214-6220
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• 2015

A track circuit has used stably more than 100 years for detecting train position, but solution of track circuit sort circuit incapacity due to a rust is necessary for side line in station yard, coast line and level crossing for conventional line in rural line. Domestically, Axle Counter System(ACS) has partially used for Hot Box System for high speed line and turnout for CBTC system. In contrast, most of countries has used ACS not only trunk line but also rural line and its application has increased for metro, electric car and industrial railway. In this paper, we has verified the operating status of ACS which installed with existing track circuit through log analsis to implement pilot application in mail track and turnout in station yard. And interface test with interlocking system has conducted at Obong shunting yard, as well as Cheongju station and has analyzed test result. Based on a test result, we made fail safe design, manufacturing skill and established system requirement specification for the smooth operation and maintenance.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.6
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• pp.1217-1223
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• 2020

The Block cipher CHAM is lightweight block cipher for low-end processors, developed by National Security Research Institute from Korea. The mode of operation is necessity for efficient operation of block cipher, among them, the counter (CTR) mode has good efficiency because it is easy to implement and supporting parallel operation. In this paper, we propose the optimized implementation for block cipher CHAM-CTR. The proposed implementation can be skipped some rounds by pre-computation. Thus it has better calculating speed than existing CHAM. Also, this implementation pre-load some of round keys to registers, before entering round functions. It makes reduced 160cycles loading time for round key load. Finally, proposed implementation achieved higher performance about 6.8%, and 4.5% for fixed-key scenario, and variable-key scenario, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.12
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• pp.1275-1280
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• 2015

A large-sized exciter that vibrates a two-ton component is required to simulate the field operating conditions of a counterweight of an excavator. However, it is difficult for a small-medium sized company to obtain a large exciter for the life test of a counterweight which is an equivalent counterbalancing weight that balances a load. Therefore, in this study, we developed life test equipment for evaluating the reliability of construction machinery weighing about two tons. It simulates the field operating conditions using rotational vibrators consisting of electric motors. A failure analysis of the counterweight was also performed for the major components. Field data acquired from various sites were applied to the life test design of the counterweight. Finally, a zero-failure qualification test based on the accelerated life test was designed, and there was no failure during the test, which guarantees a life of $B_5$ 10,000 hours.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.8
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• pp.1088-1096
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• 2006

The purpose of this study was to identify the service encounter blueprint by types of restaurants in order to manage moment of truth when customers who visit a restaurant encounter services. The service encounter blueprint gives an overall picture of the service provision to visualize an entire service process and its integrated structure. The blueprint is used for service process analysis technique. The random samples of 15 customers were observed by types of restaurants and the records were collected for three-days' observation. Interviews were performed by 3 managers, 3 service encounter employees, 3 cashiers, 3 cooks and 10 customers by types of restaurants. After drawing the first service blueprint, it was revised by the interview with the 3 managers and 6 service encounter employees. In this paper, restaurant service processes are reviewed and analyzed. By use of service blueprint, the processes are analyzed to find a fail point, customer wait, employee decision. As a result of making a blueprint of service encounter by types of restaurant, blueprints of fine-dining restaurants and family restaurants were similar, while fast-food restaurants showed a little difference. In particular, difference was indicated in a point where interaction of service encounter occurred. Difference was indicated depending on types of restaurants. Therefore, the efforts to improve this problem were needed. The blueprint is a map or flowchart (called a process chart in manufacturing) of all transactions constituting the service delivery process. The results showed that service encounter blueprint can be used to improve the service process in the restaurant's encounter.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.745-746
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.653-654
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• 2012

• Proceedings of the Korean Information Science Society Conference
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• 2008.06a
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• pp.305-306
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• 2008