• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.517-519
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• 2003

하드웨어 검증과 모델 체킹 등의 분야에서, SAT(satisfiability problem)나 항진 명제 검사(tautology checking)는 매우 중요한 문제이다. 그러나 이들은 모두 NP-complete 문제이므로 그 복잡도가 매우 크다. 이를 해결하기 위한 여러 연구가 진행되고 있고, 그 결과 성능이 좋은 solver들이 개발되었다. 하지만 문제가 커질수록 solver의 처리 시간이 급격하게 증가한다. 이 논문에서는 solver가 복잡한 문제를 더 효율적으로 풀기 위해 논문“Local search for Boolean relations on the basis of unit propagation”［5］에서 제안된 preprocessor(전처리기), P_EQ의 개념을 설명하고, 실험을 통한 결과를 제시한다.

• The Pure and Applied Mathematics
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• v.8 no.2
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• pp.163-174
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• 2001

In this paper we modify two indicators related to the global avalanche criterion (GAC) and discuss their properties. Also, we apply the modified indicators to measure the GAC of S-boxes of DES.

• The Pure and Applied Mathematics
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• v.25 no.4
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• pp.253-265
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• 2018

In this paper, we introduce the concept of Fibonacci sequences on MV-algebras and study them accurately. Also, by introducing the concepts of periodic sequences and power-associative MV-algebras, other properties are also obtained. The relation between MV-algebras and Fibonacci sequences is investigated.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.8 no.3
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• pp.39-48
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• 1998

GAC(GloabvalAvalanche Characteristics)은 부울함수가 전파특성 관점에서 얼마나 우수한지를 전체적인 관점에서 나타내는 특성으로 Zhang-Zheng(1995)에 의해서 제안되었다. GAC을 측정하는 기준으로는 와 가 있으며, 두 기준값이 작을수록 부울함수는 보다 우수한 전파특성을 갖는다. Zhang-Zheng은 GAC이 우수한 균형인 부울함수를 설계하는 두 가지 방법을 제시하였으며, 균형인 부울함수f의 대수적 차수가 3 이상일 때 의 하한이 $2^이라고 추측하였다. 본 논문에서는Zhang-Zheng의 방법보다 우수한 새로운 설계방법을 제시하며, 이를 이용하여 그들의 추측에 대한 반례를 제시한다.한다.

• Journal of the Chungcheong Mathematical Society
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• v.23 no.4
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• pp.885-892
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• 2010

In this paper we study the structures and properties of a single cycle T-finction, whose theory has been lately proposed by Klimov and Shamir. Any cryptographic system based on T-functions may be insecure. Some of the TSC-series stream ciphers have been successfully attacked by some attacks. So it is important to analyze every aspect of a single cycle T-function. We study some properties on a single cycle T-function and we show some examples are single cycle T-functions by these properties, whose proof is easier than existing methods.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.4
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• pp.535-542
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• 1986

In this paper, a hidden surface removal algorithm that generates a perspective view of three space plane-faced objects using scan line coherence is proposed. In particular, the proposed algorithm deals with hidden surface elimination of penetrating objects by using the optimum span division method with minimum test for priority test of segments. Also, a hidden surface redmoval method for representing sectional view of solids by using boolean difference is described.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.1
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• pp.89-99
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• 1993

A solid modeller was developed in this paper. Representation scheme of modelling is nonmanifold B-rep. While namy B-rep modellers use edges as basic element of modelling, this modeller is triangle-based. New modelling element, split triangle that is composed of 3 pure half-edges and has no information about the adjoining triangles, was defined to enlarge the range of representation. Corresponding algorithms for Boolean set operations were also developed.

• Journal of the Korean Institute of Landscape Architecture
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• v.30 no.1
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• pp.1-10
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• 2002

The purpose of this article is to examine land use change in the fringe area of a metropolitan city through multi-temporal data analysis. Change detection has been regarded as one of the most important applications for utilization of remotely sensed imageries. Conventionally, two images were used for change detection, and Arithmetic calculators were generally used on the process. Meanwhile, multi-temporal change detection for a large number of images has been carried out. In this paper, a digital land-use map and three Landsat TM data were utilized for the multi-temporal change detection Each urban area map was extracted as a base map on the process of multi-temporal change detection. Each urban area map was converted to bit image by using boolean logic. Various urban change types could be obtained by stacking the urban area maps derived from the multi-temporal data using Geographic Information System(GIS). Urban change type map was created by using the process of piling up the bit images. Then the urban change type map was compared with each land cover map for the change detection. Dalseo-gu of Daegu city and Hwawon-eup of Dalsung-gun, the fringe area of Daegu Metropolitan city, were selected for the test area of this multi-temporal change detection method. The districts are adjacent to each other. Dalseo-gu has been developed for 30 yeais and so a large area of paddy land has been changed into a built-up area. Hwawon-eup, near by Dalseo-gu, has been influenced by the urbanization of Dalseo-gu. From 1972 to 1999, 3,507.9ha of agricultural area has been changed into other land uses, while 72.7ha of forest area has been altered. This agricultural area was designated as a 'Semi-agricultural area'by the National landuse Management Law. And it was easy for the preserved area to be changed into a built-up area once it would be included as urban area. Finally, the method of treatment and management of the preserved area needs to be changed to prevent the destruction of paddy land by urban sprawl on the urban fringe.

• Journal of Korean Library and Information Science Society
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• v.21
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• pp.253-289
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• 1994

The purpose of this study is about the search pattern of LINNET (Library Information Network System) OPAC users by transaction log, maintained by POSTECH(Pohang University of Science and Technology) Central Library, to provide feedback information of OPAC system design. The results of this study are as follows. First, for the period of this analysis, there were totally 11, 218 log-ins, 40, 627 transaction logs and 3.62 retrievals per a log-in. Title keyword was the most frequently used, but accession number, bibliographic control number or call number was very infrequently used. Second, 47.02% of OPAC, searches resulted in zero retrievals. Bibliographic control number was the least successful search. User displayed 2.01% full information and 64.27% local information per full information. Third, special or advanced retrieval features are very infrequently used. Only 22.67% of the searches used right truncation and 0.71% used the qualifier. Only 1 boolean operator was used in every 22 retrievals. The most frequently used operator is 'and (&)' with title keywords. But 'bibliographical control number (N) and accessionnumber (R) are not used at all with any operators. The causes of search failure are as follows. 1. The item was not used in the database. (15, 764 times : 79.42%). 2. The wrong search key was used. (3, 761 times : 18.95%) 3. The senseless string (garbage) was entered. (324 times : 1.63%) On the basis of these results, some recommendations are suggested to improve the search success rate as follows. First, a n.0, ppropriate user education and online help function let users retrieve LINNET OPAC more efficiently. Second, several corrections of retrieval software will decrease the search failure rate. Third, system offers right truncation by default to every search term. This methods will increase success rate but should considered carefully. By a n.0, pplying this method, the number of hit can be overnumbered, and system overhead can be occurred. Fourth, system offers special boolean operator by default to every keyword retrieval when user enters more than two words at a time. Fifth, system assists searchers to overcome the wrong typing of selecting key by automatic korean/english mode change.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.4
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• pp.739-747
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• 2015

Masking technique that is most widely known as countermeasure against power analysis attack prevents leakage for sensitive information during the implementations of cryptography algorithm. it have been studied extensively until now applied on block cipher algorithms. Masking countermeasure have been applied to international standard SEED algorithm. Masked SEED algorithm proposed by Cho et al, not only protects against first order power analysis attacks but also efficient by reducing the execution of Arithmetic to Boolean converting function. In this paper, we analyze the vulnerability of Cho's algorithm against first order power analysis attacks. We targeted additional pre-computation to improve the efficiency in order to recover the random mask value being exploited in first order power analysis attacks. We describe weakness by considering both theoretical and practical aspects and are expecting to apply on every device equipped with cho's algorithm using the proposed attack method.