• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.5
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• pp.1001-1011
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• 2017

A lattice-based cryptography is known as one of the post-quantum cryptographies. Ring-LWE problem is an algebraic variant of LWE, which operates over elements of polynomial rings instead of vectors. It is already known that post-quantum cryptography has side-channel analysis vulnerability. In 2016, Park et al. reported a SPA vulnerability of the public key cryptosystem, which is proposed by Roy et al., based on the ring-LWE problem. In 2015 and 2016, Reparaz et al. proposed DPA attack and countermeasures against Roy cryptosystem. In this paper, we show that the chosen ciphertext SPA attack is also possible for Lyubashevsky cryptosystem which does not use NTT. And then we propose a countermeasure against CCSPA(Chosen Ciphertext SPA) attack and we also show through experiment that our proposed countermeasure is secure.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.3
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• pp.11-21
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• 2021

In the last few years, there is growing interest in the field of simultaneous equation estimation in finance due to the endogeneity problem caused by measurement errors, simultaneity, or omitted variables. This study aims to discuss the endogeneity problem in corporate financing decisions and investigate the interrelationship of financial decision-making such as investment decision, dividend decision, and external financing decision in Pakistan Stock Exchange (PSX) using two-stage least squares (2SLS) and generalized method of moment (GMM) estimation. The Bruech-Pagan test shows that the data has no heteroskedasticity issue and 2SLS is a better approach in the context of this study as compared to the GMM approach, and internal instruments are also sufficiently strong and valid. The three financial decision-making attributes are not jointly determined, and the dividend is influenced by one-sided investment. In the emerging stock market context, external financing and investment are not inter-related and did not affect each other. The question of whether the simultaneous equation estimation can be useful in the context of the emerging stock markets and newly-growing firms remains unanswered. The inclusive evidence shows that the theoretical link in the emerging stock market is difficult to prove like in developed stock markets.

• Management Science and Financial Engineering
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• v.12 no.1
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• pp.113-125
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• 2006

Bilevel programming problem is a two-stage optimization problem where the constraint region of the first level problem is implicitly determined by another optimization problem. In this paper we consider the bilevel quadratic/linear fractional programming problem in which the objective function of the first level is quasiconcave, the objective function of the second level is linear fractional and the feasible region is a convex polyhedron. Considering the relationship between feasible solutions to the problem and bases of the coefficient submatrix associated to variables of the second level, an enumerative algorithm is proposed which finds a global optimum to the problem.

• Management Science and Financial Engineering
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• v.16 no.3
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• pp.95-102
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• 2010

This paper considers the robust inventory control problem introduced by Bertsimas and Thiele [4]. In their paper, they have shown that the robust version of the inventory control problem can be solved by solving a nominal inventory problem which is formulated as a mixed integer program. As a proper generalization of the model, we consider the problem with non-stationary cost. In this paper, we show that the generalized version can also be solved by solving a nominal inventory problem. Furthermore, we show that the problem can be solved efficiently.

• Journal of Navigation and Port Research
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• v.40 no.5
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• pp.329-336
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• 2016

The overall purpose of this paper is to conduct research on alternatives for strengthening the competitiveness of a state-run shipping company, Vinalines Corporation, the largest shipping and maritime enterprise in Vietnam. The first section of the introduction gives a panoramic overview of the current development situation of the Vietnam maritime industry and Vinalines. After summarizing a literature review in section 2, some alternatives are proposed in sections 3 and 4 to overcome the current difficulties of Vinalines and to improve the corporation's competitiveness for sustainable development by utilizing linear optimization and financial analysis. The final section presents a summary and recommendation for future study. It is concluded that privatization is the key solution for every problem faced by the corporation at present. Furthermore, modification of laws, restructuring of enterprise governance, financial situation, and fleet are also extremely necessary.

• International Journal of Human Ecology
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• v.9 no.1
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• pp.81-95
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• 2008

This paper examined the impact of psychological characteristics of consumers on household debt decisions. With the use of the Heckit models (the traditional approach to the selection problem) this study undertook an empirical study of the influence of a wide range of factors on financial decisions. This study used U.S. household-level data that offers detailed information on household debt, expectations about future income, expectations about future economic conditions, the amount of financial risk the respondent was willing to take, and the amount of time allotted for planning family savings and spending. This study showed that respondents with both substantial financial risk tolerance and positive expectations about future income were likely to have larger household debt showing that researchers and policy-makers need to consider consumer sentiment and preference measures in modeling behavior in credit markets. Additional results showed that household debt is significantly related to two key economic variables: income and net worth.