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A Practical Implementation of Fuzzy Fingerprint Vault
( Sungju Lee ),( Yongwha Chung ),( Daesung Moon ),( Sung Bum Pan ),( Chang-ho Seo ) 한국인터넷정보학회 2011 KSII Transactions on Internet and Information Syst Vol.5 No.10
Recently, a cryptographic construct, called fuzzy vault, has been proposed for crypto-biometric systems, and some implementations for fingerprint have been reported to protect the stored fingerprint template by hiding the fingerprint features. In this paper, we implement the fuzzy fingerprint vault, combining fingerprint verification and fuzzy vault scheme to protect fingerprint templates. To implement the fuzzy fingerprint vault as a complete system, we have to consider several practical issues such as automatic fingerprint alignment, verification accuracy, execution time, error correcting code, etc. In addition, to protect the fuzzy fingerprint vault from the correlation attack, we propose an approach to insert chaffs in a structured way such that distinguishing the fingerprint minutiae and the chaff points obtained from two applications is computationally hard. Based on the experimental results, we confirm that the proposed approach provides higher security than inserting chaffs randomly without a significant degradation of the verification accuracy, and our implementation can be used for real applications.
Sungju Choi,Youngjin Kang,Jonghwa Kim,Jungmok Kim,Sung-Jin Choi,Dong Myong Kim,Ho-Young Cha,Hyungtak Kim,Dae Hwan Kim 대한전자공학회 2015 Journal of semiconductor technology and science Vol.15 No.5
It is essential to acquire an accurate and simple technique for extracting the interface trap density (Dit) in order to characterize the normally-off gate-recessed AlGaN/GaN hetero field-effect transistors (HFETs) because they can undergo interface trap generation induced by the etch damage in each interfacial layer provoking the degradation of device performance as well as serious instability. Here, the frequency-dependent capacitance-voltage (C-V) method (FDCM) is proposed as a simple and fast technique for extracting Dit and demonstrated in normally-off gate-recessed AlGaN/GaN HFETs. The FDCM is found to be not only simpler than the conductance method along with the same precision, but also much useful for a simple C-V model for AlGaN/GaN HFETs because it identifies frequency-independent and biasdependent capacitance components.
The Generalized Lorenz Systems: A New Testbed Model for Data Assimilation
Sungju Moon,Jong-Jin Baik 한국기상학회 2021 한국기상학회 학술대회 논문집 Vol.2021 No.10
The feasibility of using a (3N)-dimensional generalization of the Lorenz system in testing a data assimilation method is explored through numerical experiments. The generalization extends the Lorenz system, known as the Lorenz "63 model, into a (3N)-dimensional nonlinear system for any positive integer N, which is known to exhibit chaos synchronization. Because the extension involves inclusion of additional wavenumber modes, raising the dimension allows the system to resolve smaller-scale motions, a unique characteristic of the present generalization that can be relevant to real modeling scenarios. Accordingly, model imperfections are simulated by assuming a high-dimensional generalized Lorenz system as the true system and a generalized system of dimension less than or equal to the dimension of the true system as the model system. The Ensemble Kalman filter data assimilation method is tested. Different scenarios relevant to data assimilation practices are simulated by varying the dimensional differences between the model and true systems, ensemble size, and observation frequency and accuracy. The results indicate that this generalization of the Lorenz system is a viable and flexible tool for evaluating the effectiveness of data assimilation methods and, therefore, a meaningful addition to the portfolio of testbed systems that includes the Lorenz "63 and "96 models, especially considering its relationship with the Lorenz "63 model
High-Dimensional Lorenz Systems, Atmospheric Predictability, and Data Assimilation: An Overview
Sungju Moon 한국기상학회 2021 한국기상학회 학술대회 논문집 Vol.2021 No.10
In this talk, I will give a broad overview of my PhD project. The primary aim has been to investigate chaotic or nonlinear dynamical behavior of certain high-dimensional extensions of the Lorenz system and to explore potential implications pertaining to the study and modeling of Earth"s atmosphere and its predictability. To this end, two distinct approaches to extending the Lorenz system were employed: 1. incorporating additional physical ingredients in the governing equations, leading to the 6-dimensional physically extended Lorenz system and 2. including higher wavenumber modes before truncating the series expansions in the derivation, yielding the (3N)- and (3N+2)-dimensional generalized Lorenz systems for any positive integer N. The newly derived systems are thoroughly analyzied, utilizing various tools borrowed from the study of dynamical systems. I will first go over the results deemd most important from the chaos theoretic point of view, which includes the discovery of a new chaotic attractor, analysis of coexisting attractors, and some new insights into chaos synchronization in these systems. Inspired in particular by the chaos synchronization result, I will then argue that the generalized systems can be used as a testbed model for assessing data assimilation methods with some distinctive advantages compared to other conventional testbed models. Predictability has also been an important theme; more specifically, my aim has been to explore and establish deviation time as the measure of predictability more in tune with the chaos inherent to Earth"s atmosphere, which has thus far been overlooked in favor of other notions of predictability. Upon testing the deviation time concept on the generalized Lorenz systems as well as on realistic simulations of a precipitating case over East Asia by the Weather Research and Forecast (WRF) Model, it was suggested that atmospheric predictability may not necessarily respond monotonically to refinements of vertical resolution. I will conclude the talk with suggestions for future research.
Sungju Choi,Juntae Jang,Hara Kang,Ju Heyuck Baeck,Jong Uk Bae,Kwon-Shik Park,Soo Young Yoon,In Byeong Kang,Dong Myong Kim,Sung-Jin Choi,Yong-Sung Kim,Oh, Saeroonter,Dae Hwan Kim IEEE 2017 IEEE electron device letters Vol.38 No.5
<P>We propose an experimental method to decompose the positive gate-bias stress (PBS)induced threshold voltage shift (AVth) of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) into the contributions of distinct degradation mechanisms. Topgate self-aligned coplanar structure TFTs are used for this letter. Stress-time-divided measurements, which combine the subgap density-of-states (DOS) extraction and the analysis on recovery characteristics, are performed to separate the AVth components. Change in excess oxygen (Oex)-related DOS is clearly observed, and AVth by PBS is quantitatively decomposed into the contributions of the active Oex, and the deep and shallow gate insulator traps. The quantitative decomposition of PBS-induced AVth provides physical insight and key guidelines for PBS stability optimization of a-IGZO TFTs.</P>