• 한국전자거래학회지
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• 제4권1호
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• pp.103-115
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• 1999

The electronic cash, an electronic equivalent of the real paper money, has been recently proposed as one of the various payment methods for electronic commerce. In this paper, we design an electronic cash payment system based on a new electronic cash payment protocol that can effectively provide full anonymity and avoid double-spending. The protocol is suitable for use as the electronic cash control or electronic cash database. The protocol support also security and electronic cash property.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권7호
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• pp.3733-3755
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• 2019

E-cash has its merits comparing with other payment modes. However, there are two problems, which are how to achieve practical/complete tracing and how to achieve it in compact E-cash. First, the bank and the TTP (i.e., trusted third party) have different duties and powers in the reality. Therefore, double-spending tracing is bank's task, while unconditional tracing is TTP's task. In addition, it is desirable to provide lost-coin tracing before they are spent by anyone else. Second, compact E-cash is an efficient scheme, but tracing the coins from double-spender without TTP results in poor efficiency. To solve the problems, we present a compact E-cash scheme. For this purpose, we design an embedded structure of knowledge proof based on a new pseudorandom function and improve the computation complexity from O(k) to O(1). Double-spending tracing needs leaking dishonest users' secret knowledge, but preserving the anonymity of honest users needs zero-knowledge property, and our special knowledge proof achieves it with complete proofs. Moreover, the design is also useful for other applications, where both keeping zero-knowledge and leaking information are necessary.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권4호
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• pp.1266-1285
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• 2022

Compact E-cash is the first scheme which can withdraw 2^l coins within 𝒪(1) operations and then store them in 𝒪(𝑙) bits. Because of its high efficiency, a lot of research has been carried out on its basis, but no previous research pay attention to the privacy of payees and in some cases, payees have the same privacy requirement as payers. We propose a double-blind compact E-cash scheme, which means that both the payer and the payee can keep anonymous while spending. In our scheme, the payer and the bank cannot determine whether the payees of two different transactions are the same one and connect the payee with transactions related to him, in this way, the privacy of the payee is protected. And our protocols disconnect the received coin from previous transaction, then, the coin can be transferred into an unspent coin which belongs to the payee. The proposed e-cash scheme is secure within y-DDHI and LRSW assumption.

• 재무관리논총
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• 제10권1호
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• pp.249-269
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• 2004

Free cash flow is known as a typical type of agency conflict between managers and shareholders in a firm. The insurance industry, which is not growing, is particularly susceptible to such excessive cash flow. We herein investigate the effects of stock ownership plans on reducing agency conflicts. We adopt undistributed cash flow to proxy free cash flow, and size, default risk, group membership, leverage, investment opportunity, and stock options are selected as explanatory variables. We find that stock option plans are effective(at a 10% level) in reducing free cash flow.

• 국제학술발표논문집
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• The 5th International Conference on Construction Engineering and Project Management
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• pp.243-251
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• 2013

Cash management is a major concern for all contractors in the construction industry. It is arguable that cash is the most critical resource of all. A contractor needs to secure sufficient funds to navigate the project to the end, while keeping an eye on maximizing profits along the way. Past research attempted to address such topic via developing models to tackle the time-cost tradeoff problem, cash flow forecasting, and cash flow management. Yet, little was done to integrate the three aspects of cash management together. This paper, as such, presents a comprehensive model that integrates the time-cost tradeoff problem, cash flow management, and cash flow forecasting. First, the model determines the project optimal completion time by considering the different alternative construction methods available for executing project activities. Second, it investigates different funding alternatives and proposes a project-level cash management plan. Two funding alternatives are considered; they are borrowing and company own financing. The model was built as a combinatorial optimization model that utilizes ant colony search capabilities. The model also utilizes Microsoft Project software and spreadsheets to maintain an environment that incorporates activities, their durations, and other project data, in order to estimate project completion time and cost. Ant Colony Optimization algorithm was coded as a Macro program using VBA. Finally, an example project was used to test the developed model, where it acted reliably in maximizing the contractor's profit in the test project.

• Journal of Communications and Networks
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• 제4권2호
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• pp.81-89
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• 2002

In this paper, we design and implement an efficient fair off-line electronic cash system based on Elliptic Curve Discrete Logarithm Problem (ECDLP), in which the anonymity of coins is revocable by a trustee in case of dispute. To achieve this, we employ the Petersen and Poupard s electronic cash system [1] and extend it by using an elliptic curve over the finite field GF($2^n$). This naturally reduces message size by 85% compared with the original scheme and makes a smart card to store coins easily. Furthermore, we use the Baek et al. s provably secure public key encryption scheme [2] to improve the security of electronic cash system. As an extension, we propose a method to add atomicity into new electronic cash system. To the best of our knowledge, this is the first result to implement a fair off-line electronic cash system based on ECDLP with provable security.

• 한국정보보호학회:학술대회논문집
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• 한국정보보호학회 2002년도 종합학술발표회논문집
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• pp.266-269
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• 2002

As a simulation or replacement of analog money in cyber space, the e-cash was introduced by using cryptographic primitives. Since a perfect anonymity system causes some illegal activities, such as money laundering, blackmailing, and illegal purchase, a revocable electronic system was paid a great attention to control the anonymity. In general, Trust Third Party(TTP) is introduced to detect any dubious user and coin, namely user tracing and coin tracing. In this paper we propose a new revocable anonymity e-cash system, and verify the security requirement as well. In our scheme a user first withdraws the e-coin from bank by using blind signature, and then TTP verifies the bank's signature and records the tracing information.

• 대한안전경영과학회지
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• 제15권4호
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• pp.435-448
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• 2013

The aim of this study is to investigate and develop the extended models for Economic Cash Amount(ECA), Cash Break Even-Point(BEP), and Cash Flow Statement(CFS) by referencing systematic literature review in the field. The study develops three extended models to determine the optimal cash amount: ECA model with interest opportunity cost, financing transaction cost and financing fail cost, ECA model with daily cash supply and interest opportunity cost, ECA model with financing fail cost and interest opportunity cost. Earnings Before Interests, Tax, Depreciation and Amortization(EBITDA) is obtained by subtracting noncash depreciation costs from Earning Before Interest and Tax(EBIT), which is efficient metric to evaluate operating cash flow. The research also develops two extended Cash BEP models, considered as interest and corporate tax, in order to indentify the break-even point as EBITDA equals zero. Furthermore, this paper proposes the modified version of CFS by introducing the reclassification of operating and financing accounts in the statement of financial position. In addition, the study also present the reclassification of five types of profit, such as gross profit, EBIT, ordinary profit, special profit, and net profit within the statement of comprehensive income. In order to provide a better understanding of the proposed cash flow models, numerical examples, such as two-sample t test and Analysis of Variance(ANOVA), are presented to demonstrate the statistical significance according to the industrial types for net working capital(i.e cash-to-cash), net profit, operating cash flow and free cash flow.

• 한국정보과학회논문지:시스템및이론
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• 제26권7호
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• pp.839-846
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• 1999

전자상거래에서 중요한 지불 수단으로 떠오르고 있는 전자화폐 시스템에 있어서 사용자에의 익명성 제공은 기존의 지불 시스템에서 제공하지 못하는 중요한 요소이다. 그러나 사용자 익명성을 악용하여 각종 범죄 활동에 이용하려는 시도가 발생할 수 있으며 전자화폐 시스템 도입시 이에 대한 대책도 함께 강구되어야 한다. 따라서 본 논문에서는 전자화폐의 효율적 사용을 위해 분할성 기능과 함께 화폐 추적과 사용자 추적 기능을 제공하는 효율적인 전자화폐 프로토콜을 제안한다.Abstract Electronic Cash System is an important payment method in Electronic Commerce. The anonymity of users is an important issue in such systems, but the issue has not been addressed by previous payment methods. User anonymity can lead to a system that is vulnerable to various criminal activities. Therefore, e-cash systems must consider ways to prevent such criminal activities. In this paper we suggest an efficient e-cash system that eliminates the vulnerability of the system by using the divisible ability of the system with the coin and owner tracing.

• 한국전자거래학회지
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• 제24권1호
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• pp.91-103
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• 2019

기업 입장에서 앞으로 있을 현금흐름에 대한 예측이란, 향후 발생할 수 있는 유동성(현금부족) 위험을 미리 파악할 수 있다는 점과 미래의 투자계획을 세우는데 중요한 자료가 될 수 있다는 점에서 중요한 의의를 지닌다. 그러나 기업 간 거래에서 매출 채권 형태로 발생하는 거래 유형은 다른 유형의 거래와는 달리 채무 이행 불확실성이 존재하며, 이로 인해 정확한 현금흐름 예측을 어렵게 한다. 본 연구에서는 추계적 분석 기법의 하나인 가변 마코프 기법(Variable Order Markov model)을 활용하여 기업 간에 발생 할 수 있는 매출 채권과 관련한 현금흐름 동향을 예측한다. 구체적으로는, PST(Probabilistic Suffix Tree)라는 가변 마코프 기법을 활용하여, 지난 과거의 매출 채권 발행 및 수금 내역을 바탕으로 해당 매출 채권들의 기대 연령 예측 연구를 수행하였다. 본 연구결과를 통해, 기존의 다른 기법들과 대비하여 가변 마코프 기법을 활용 시, 평균 12.5% 이상의 정확도를 보여주고 있음을 밝혔다.