• Journal of the Korea Institute of Information Security & Cryptology
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• v.31 no.1
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• pp.1-9
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• 2021

This paper proposes to automate the process of predicting crypto-operations from the power signal generated in RSA decoding process by frequency analysis and K-means algorithm. RSA decoding process is divided into square and multiply operation, and if we can predict the type of operations over time, we will know the RSA key value. After converting the power signal generated in the process of decoding into two-dimensional frequency signal, this paper used K-means algorithm to classify the frequency vector according to the type of operation. these classified frequency vector were used to predict the types of operations.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.34-40
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• 2006

For a cooling performance research of the combustor operated in a extreme environment of a high temperature and high pressure, we accomplished a cooling performance analysis. Generally a heat transfer characteristic in cooling passage is known well experimentally and theoretically, however heat flux in the combustion chamber isn't. In this study, fluid flow combined with heat transfer and thermal structural analysis is accomplished about a combustor nozzle. We tried to analyze the cooling performance with a heat transfer characteristic of a gas and coolant side in the view point of quantity on the mass flow rate to be supplied to the cooling channel. And finally, evaluation on the thermal and structural safety of nozzle wall material was accomplished.

• Korean Journal of Environment and Ecology
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• v.26 no.6
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• pp.884-891
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• 2012

The characteristic of fish fauna and distribution by habitat type in the Yanghwa stream were investigated from August, 2008 to June, 2009. During the surveyed period, 30 species belonging 8 families were collected. And there were 10 Korea endemic species(33.3%), including Rhodeus uyekii et and so on. Dominant species was Rhodeus notatus, and subdominant species was Pseudorasbora parva. Dominant species according to habitat type was Pseudorasbora parva in Dam type pool and Channel conected pool, Pseudogobio esocinus(Run), Zacco platypus(Riffle), Rhodeus notatus(Side channel and Substrate type pool), Squalidus gracilis majimae(Meander type pool), and Carassius auratus(Channel unconnected pool), respectively. As a results of community analysis in the Yanghwa Stream, diversity, richness, and abundance indices showed relatively high values, indicating that studied stream have relatively stable community structure. Moreover, cluster and principal component analysis were divided by two groups(lotic and lentic habitats), suggest that species and individuals were different among habitat types.

• Journal of Energy Engineering
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• v.17 no.2
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• pp.116-123
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• 2008

In order to study the heat transfer, effectiveness and pressure drop of an internal heat exchanger (IHX) for $CO_2$, heat pump under heating condition, the experiment and numerical analysis were performed. Four kinds of IHXs were used. The section-by-section method and Hardy-Cross method were used for the numerical analysis. The effects of IHX on the flow rate of refrigerant, the IHX length, the operating condition of a gas-cooler and an evaporator and the type of IHXs were investigated. With increasing the flow rate, the heat transfer rate increased about 25%. The heat transfer of the micro-channel tube was larger about 100% than that of the coaxial tube. With increasing the IHX length, the heat transfer rate decreased. The low-side pressure drop was larger compared with that of the high-side. And the pressure drop of the microchannel tube was larger about 100% than that of the coaxial tube. With increasing the high-side temperature and decreasing the low-side temperature, the heat transfer rate increased about 3%. From this study, we can see that new correlation on $CO_2$ heat transfer characteristics and tube type is necessary.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.5
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• pp.993-1000
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• 2017

When the availability of embedded device is considered, combined countermeasure such as first-order masking and hiding countermeasures is quite attractive because the security and efficiency can be provided at the same time. Especially, combined countermeasure can be applied to the confusion and diffusion layers of the first and last rounds in order to provide the efficiency. Also, the middle rounds only employs first-order masking countermeasure or no countermeasure. In this paper, we suggest a novel side channel analysis with low complexity in the output of diffusion layer. In general, the attack target cannot be set to the output of diffusion layer owing to the high complexity. When the diffusion layer of block cipher is composed of AND operations, we show that the attack complexity can be reduced. Here, we consider that the main algorithm is SEED. Then, the attack complexity with $2^{32}$ can be reduced by $2^{16}$ according to the fact that the correlation between the combination of S-box outputs and that of the outputs of diffusion layer. Moreover, compared to the fact that the main target is the output of S-box in general, we demonstrate that the required number of traces can be reduced by 43~98% in terms of simulated traces. Additionally, we show that only 8,000 traces are enough to retrieve the correct key by suggested scheme, although it fails to reveal the correct key when performing the general approach on 100,000 traces in realistic device.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.2
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• pp.308-315
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• 2014

The aims of this study are to analysis about surface muscle activity of lower and upper musculus erector spinae according to walkers form. The subjects of the current step is inconvenient to use a walker and five people over the age of 65 valid samples were selected as final. All the subjects were measured in three forms. Wireless EMG muscle activity is a measure of surface measurements were measured using a system, both musculus vastus lateralis, outside the erector spinae muscle, musculus biceps femoris, gastrocnemius muscle was attached to the channel electrodes. According to the results, First, gastrocnemius muscle activity showed significant differences by type of gait. Second, the muscle activity of the erector spinae muscle walking showed significant differences by type, side grip type showed the lowest muscle activity. Consequently, the present study is the efficient use of the four-wheel walker will provide the baseline data.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.49 no.3
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• pp.74-80
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• 2012

Recently at SCIS2011, Nakatsu et. al. proposed multi-round Correlation Power Analysis(CPA) on Hardware Advanced Encryption Standard(AES) to improve the performance of CPA with limited number of traces. In this paper, we propose, Multi-Round CPA to retrieve master key using CPA of 1round and 2round on Hardware DES. From the simulation result for the proposed attack method, we could extract 56-bit master key using the 300 power traces of Hardware DES in DPA contes. And it was proved that we can search more master key using multi-round CPA than using single round CPA in limited environments.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.37.1-37.1
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• 2013

We present our study of analyzing the photometric properties of the globular cluster (GC) system which resides in the extended halo of the central bright Coma cluster galaxy NGC 4874. The core of the Coma cluster of galaxies (Abell 1656) was observed with both the HST Advanced Camera for Surveys (ACS) in the F475W (g475) and F814W (I814) and Wide Field Camera 3 IR Channel (WFC3/IR) in the F160W (H160) filters. The data analysis procedure and GC candidate selection criteria are briefly described. We investigate the interesting "tilt" features in color-magnitude diagrams for this GC system and their link to the nonlinear color-metallicity relation for GCs. The NGC 4874's GC system exhibits a bimodal distribution in the optical g475-I814 color and much more than half the GCs fall in the red side at g475-I814 ~ 1.1. This bimodality is weakened in the optical-IR I814-H160 color; the quantitative analysis on the features of both color distributions using the Gaussian Mixture Modeling code proves the bimodalities are different. Both colors, thus, cannot linearly reflect the bimodality of an underlying metallicity, supporting the suggestion that observed bimodalities in extragalactic GC colors are the metallicity-to-color projection effect.

• Annals of Clinical Neurophysiology
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• v.4 no.1
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• pp.28-33
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• 2002

Backgrounds and objective : EEG reflect dynamic changes of continuous neuronal activities by internal and external stimuli. The aim of this study is to quantify nonlinearly the local dynamic differences among EEG data corresponding to different states of brain. Methods : EEG was recorded from twelve healthy normal subjects(mean age, 29.7 years; 8 men and 4 women) using digital EEG machine. 18-channel EEG data were selected during eyes closed(EC), eyes open(EO), and mental arithmetic(MA) in each subject. Correlation dimension(D2) and largest Lyapunov exponent(LLE) were calculated from three states and average value was mapped 2 dimensionally and compared with each other. Results : The distribution of D2 was relatively symmetric and its value was higher in frontal than in parieto-occipital region during EC. These findings were reversed during EO. Bilateral centro-temporo-parietal region showed high D2 value in MA compared with those in EC, which was more prominent in left side. LLE was larger than zero in all state and showed significant differences among EC, EO and MA(p=0.000). Conclusion : These results suggest that nonlinear analysis of EEG can quantify dynamic state of brain.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.4
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• pp.803-807
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• 2018

The Fantomas and the Robin are the block ciphers included in the LS-designs, the family of block ciphers. They are designed to efficiently apply the masking technique, which is a side-channel analysis countermeasure technique, using L-boxes and S-boxes capable of bit slice implementation. In this paper, we show that the key recovery attacks of Fantomas and Robin through the related-key differential analysis are possible with $2^{56}$ and $2^{72}$ time complexity, $2^{56}$ and $2^{69}$ chosen plaintext respectively.