• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.1254-1257
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• 2007

유비쿼터스 환경이 구축됨에 따라서 온라인상에서 사용자를 인증하고 적합한 서비스를 제공할 수 있도록하기 위하여 OTP(One-Time Password)에 대한 연구가 활발히 진행되고 있다. 하지만 ID와 고정된 패스워드의 대안으로 연구되고 있는 OTP 또한 중간자공격에 취약하여 패스워드 노출 문제가 발생하고, 기존의 사용되고 있는 방식이 6~8자리의 OTP를 사용하고 있기 때문에 자릿수를 알았을 경우 사전공격 및 추측 공격이 가능할 수 있다. 기존의 OTP는 OATH와 RSA에서 연구하고 있어 두 가지 표준으로 구분된다. 그 중 OATH에서 연구하고 있으며 RFC 4226에 기술되어 있는 HOTP는 Hash-based MAC을 이용하여 안전한 OTP를 생성하고 있다 하지만 HOTP도 자릿수(Digit)가 고정되어 있어 사전 공격 및 추측 공격에 취약할 수 있다. 따라서 본 방식은 HOTP의 자릿수를 가변적으로 생성하는 R(Random digit)-OTP를 생성함으로써 제 3자의 공격으로부터 안전하게 하였다.

• Communications of the Korean Institute of Information Scientists and Engineers
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• v.31 no.9
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• pp.61-68
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• 2013

• Journal of the Korea Society of Computer and Information
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• v.16 no.2
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• pp.183-191
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• 2011

Recently Wang-Li proposed the remote user authentication scheme using smart cards. But the proposed scheme has not been satisfied security requirements considering in the user authentication scheme using the password based smart card. In this paper, we described the Wang-Li and Yoon et al.'s authentication scheme simply, and we prove that the Wang-Li's scheme is vulnerable to a password guessing attack and impersonation attack in case that the attacker steals the user's smart card and extracts the information in the smart card. Accordingly, we propose the improved user authentication scheme based on the hash function and generalized ElGamal signature scheme that can withstand many possible attacks including a password guessing attack, impersonation attack and replay attack, and that can offer the function of forward secrecy. The result of comparative analysis, the our proposed scheme is much more secure and efficient than the Wang-Li and Yoon et al.'s scheme.

• School Mathematics
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• v.11 no.1
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• pp.55-70
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• 2009

The purpose of this study is to implement Lakatos method in the teaching and learning of geometry for middle school students. In his landmark book , Lakatos suggested the following instructional approach: an initial conjecture was produced, attempts were made to prove the conjecture, the proofs were repeatedly refuted by counterexamples, and finally more improved conjectures and refined proofs were suggested. In the study, students were selected from the high achieving students who participated in the special mathematics and science program offered by the city council of Seoul. The students were given a contradictory geometric proposition, and expected to find the cause of the fallacy. The students successfully identified the fallacy following the Lakatos method. In this process they also set up a primitive conjecture and this conjecture was justified by the proof and refutation method. Some implications were drawn from the result of the study.

• School Mathematics
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• v.15 no.3
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• pp.651-665
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• 2013

The aim of this study is to find how unformal proof activities contribute to solving problems successfully and to confirm the role of teachers in the progress. For this, we developed a task that can help students communicate actively with the concept of unformal proof activities and conducted a case lesson with 6 graders in Elementary school. The study shows that unformal proof activities contribute to constructing representations which are needed to solve math problems, setting up plans for problem-solving and finding right answers accordingly as well as verifying the appropriation of the answers. However, to get more out of it, teachers need to develop a variety of tasks that can stimulate students and also help them talk as actively as they can manage to find right answers. Furthermore, encouraging their guessing and deepening their thought with appropriate remarks and utterances are also very important part of what teachers need to have in order to get more positive effect from these activities.

• Journal of the Korea Society of Computer and Information
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• v.15 no.2
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• pp.119-125
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• 2010

Recently Hsiang-Shih proposed the user authentication scheme to improve Yoon et al's scheme. But the proposed scheme has not been satisfied security requirements considering in the user authentication scheme using the password based smart card. In this paper, we proved that Hsiang-Shih's scheme is vulnerable to the off-line password guessing attack. In other words, the attacker can get the user's password using the off-line password guessing attack on the scheme when the attacker steals the user's smart card and extracts the information in the smart card. Also, the improved scheme based on the hash function and random number was introduced, thus preventing the attacks, such as password guessing attack, forgery attack and impersonation attack etc. And we suggested the effective mutual authentication scheme that can authenticate each other at the same time between the user and server.

• Journal of the Korea Society of Computer and Information
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• v.15 no.3
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• pp.91-97
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• 2010

Recently Hu-Niu-Yang proposed the user authentication scheme to improve Liu et al's scheme. But the Hu-Niu-Yang's scheme has not been satisfied security requirements considering in the user authentication scheme using the password based smart card. In this paper, we proved that Hu-Niu-Yang's scheme is vulnerable to the off-line password guessing attack in case that the attacker steals the user's smart card and extracts the information in the smart card. Also, the improved user authentication scheme solving the security vulnerability was introduced, thus preventing the attacks, such as password guessing attack, forgery attack impersonation attack, and replay attack. For preventing those attacks, the our proposed scheme need more hash functions and exclusive-OR operations than Hu-Niu-Yang's scheme.

• Journal of Digital Convergence
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• v.8 no.2
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• pp.43-54
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• 2010

While entrepreneurship is touted as an opportunity for women to exploit opportunities that are often not available in the traditional workplace, the rate of participation in entrepreneurship is lower for women than it is for men. What remains relatively unclear are the reasons that make this so. This regional study addresses this deficiency by examining two lines of thought related to entrepreneurial adoption: (1) the personal traits thought to contribute to entrepreneurship, and (2) the rational decision making processes that are believed to form a basis for entrepreneurial endeavors. My results find men and women to be different in both respects, with ambiguity tolerance, internal locus of control, perceived effectiveness of entrepreneurship, and having an entrepreneurial parent all positively predicting entrepreneurial intention for men. For women, perceived effectiveness of entrepreneurship and achievement motivation predict entrepreneurial intention. Women also rate the potential reward of entrepreneurship as significantly lower than do men, possibly because women entrepreneurs objectively face more obstacles than men with regard to obtaining financing and other stakeholder relations.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.11
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• pp.503-510
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• 2013

Recently, the rapid development of network technology has enabled people to use various services on the internet. However, the existing password-based user authentication system used in the internet environment requires a password table, which is a potential security threat as it could be leaked by an insider. To solve this issue, remote user authentication methods that do not require a user password table have been proposed. Regarding remote user authentication using a smart card in particular, various methods have been suggested to reduce expenses and to improve stability and efficiency, but the possibility of impersonation attacks and password-guessing attacks using information saved in a user's smart card still exist. Therefore, this study proposes a remote user authentication method that can safeguard against impersonation attacks and password guessing attacks, by analyzing weak points of conventional methods and creating a smart card's ID and password that are based on the user's ID and password.

• Journal of the Korea Society of Computer and Information
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• v.17 no.2
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• pp.159-166
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• 2012

Many biometrics-based user authentication schemes using smart cards have been proposed to improve the security weaknesses in user authentication system. In 2010, Chang et al. proposed an improved biometrics-based user authentication scheme without concurrency system which can withstand forgery attack, off-line password guessing attack, replay attack, etc. In this paper, we analyze the security weaknesses of Chang et al.'s scheme and we have shown that Chang et al.'s scheme is still insecure against man-in-the-middle attack, off-line biometrics guessing attack, and does not provide mutual authentication between the user and the server. And we proposed the improved scheme to overcome these security weaknesses, even if the secret information stored in the smart card is revealed. As a result, the proposed scheme is secure for the user authentication attack, the server masquerading attack, the man-in-the-middle attack, and the off-line biometrics guessing attack, does provide the mutual authentication between the user and the remote server. And, in terms of computational complexities, the proposed scheme is more effective than Chang et al.'s scheme.