• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.28 no.4
• /
• pp.809-826
• /
• 2018

The entropy evaluation method for noise sources is one of the evaluation methods for the random number generator that is the essential element of modern cryptographic systems and cryptographic modules. The primary entropy evaluation methods outside of the country are more suitable to apply to hardware noise sources than software noise sources, and there is a difficulty in quantitative evaluation of entropy by software noise source. In this paper, we propose an entropy evaluation method that is suitable for software noise sources, considering characteristics of software noise sources. We select time-dependent noise sources that are software noise sources of Windows OS, and the heuristic analysis and experimental analysis are performed considering the characteristics of each time-dependent noise source. Based on these analyses, we propose an entropy harvest method from the noise source and the min-entropy estimation method as the entropy evaluation method for time-dependent noise sources. We also show how to use our entropy evaluation method in the Conditioning Component described in SP 800-90B of NIST(USA).

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.9 no.10
• /
• pp.3945-3964
• /
• 2015

Since the decentralized structure and the blindness of a large-scale wireless network make it difficult to collect the real-time channel state or other information from random distributed relays, a fundamental question is whether it is feasible to perform the relay selection without this knowledge. In this paper, a Slotted ALOHA based Greedy Relay Selection (SAGRS) scheme is presented. The proposed scheme allows the relays satisfying the user's minimum transmission request to compete for selection by randomly accessing the channel through the slotted ALOHA protocol without the need for the information collection procedure. Moreover, a greedy selection mechanism is introduced with which a user can wait for an even better relay when a suitable one is successfully stored. The optimal access probability of a relay is determined through the utilization of the available relay region, a geographical region consisting of all the relays that satisfy the minimum transmission demand of the user. The average number of the selection slots and the failure probability of the scheme are analyzed in this paper. By simulations, the validation and the effectiveness of the SAGRS scheme are confirmed. With a balance between the selection slots and the instantaneous rate of the selected relay, the proposed scheme outperforms other random access selection schemes.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.5B
• /
• pp.365-377
• /
• 2006

We define the incomplete medium sharing system as a multi-channel shared medium communication system where any types of constraints are imposed to the set of channels that may be allocated to any transmitter-receiver node pair. A set of distributed MAC schemes are proposed, all of which are based on the CSMA/CA scheme employed in IEEE 802. 11 WLAN standards. Distributed MAC schemes are proposed in three different forms, which can be differentiated by the number and the location of back-off timers; that is, (1) one timer for all queues destined for different receiver nodes, (2) multiple timers at individual transmission queues, (3) multiple timers for individual channels. Through an extensive set of computer simulations, the performances of the proposed MAC schemes show that the MAC scheme with timers at individual transmission queues outperform the others in terms of throughput and delay for most cases considered. The complexity of the proposed schemes is also compared, and the first scheme obviously turned out to be the simplest, and the complexity of the second and third schemes depends on the number of receiver nodes and the number of channels, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.3A
• /
• pp.184-194
• /
• 2005

One of the most important factors that decide the overall performance of RFID system is anti-collision algorithm. By enhancing the anti-collision algorithm, we can increase the number of RFID tags that can be processed in unit time. Two anti-collision algorithms are most widely prevailed: one is ALOHA-based protocol and the other is a binary tree walking method, but these are still under research. In this paper, we suggest an anti-collision algorithm named AAC(Address Allocating and Calling) using pre-distributed random address, which is much faster and more efficient than existing ones. Finally, we evaluate our scheme using mathematical analysis and computer simulation.

• Health Policy and Management
• /
• v.11 no.4
• /
• pp.88-108
• /
• 2001

Separation of prescribing and dispensing practice in Korea has changed the service pattern of the pharmacy. The prescription dispensing activities, however, are concentrated excessively on the pharmacies near hospitals or clinics. Thus this study was conducted to estimate the number of optimal dispensing cases for the community pharmacy. Forty-six pharmacies were selected using systematic stratified random sampling method, and ninety-five pharmacists were interviewed on their workload of dispensing and other activities at pharmacies. One hundred and seventy prescriptions were chosen based on the length of drug administration and drug dosage form, and the dispensing time was measured by time-watch method. Also pharmacy benefit claims data were analyzed to identify the characteristics of the pharmacies which performed more than optimal dispensing cases. According to the study results, the average work time per pharmacist per day was found to be 10hours 32minutes and the dispensing activities occupied 7hours 36minutes. It took 5.72minutes on average for each dispensing case. The optimal dispensing case was estimated as 75 cases under the condition of 10hours 32minutes work time and 6% allowance rate. Even though the pharmacies near hospitals or clinics participated dispensing services actively, only pharmacies near clinics dealt with more than optimal dispensing cases. For the pharmacies near hospitals they dealt with less than optimal cases, but drug administration period per prescription was almost 3 times longer than that of pharmacies near clinics. Thus the intensity of dispensing activities such as drug administration period is to be considered to estimate optimal dispensing cases more accurately.

• Journal of the Korea Convergence Society
• /
• v.10 no.12
• /
• pp.63-69
• /
• 2019

Using a smartphone allows quick and easy authentication and payment. However, smartphone security threats are evolving into a variety of new hacking technologies, and are changing to attacks specific to the mobile environment. Therefore, there is a demand for an authentication method suitable for a mobile environment. In order to solve security weaknesses in knowledge-based authentication, many companies provide two-step authentication services such as OTP(One Time Password) to provide authentication services such as finance, games, and login. Although OTP service is easy to use, it is easy to duplicate random number table and has a disadvantage that can be reused because it is used as valid value within time limit. In this paper, we propose a mechanism that enables users to quickly and easily authenticate with high security using the authentication method that recognizes special characters through smartphone's dedicated application.

• Convergence Security Journal
• /
• v.4 no.3
• /
• pp.19-25
• /
• 2004

This research develops an algorithm using image synthesis for a server to authenticate users and implements it. The server creates cards with random dots for users and distribute them to users. The server also manages information of the cards distributed to users. When there is an authentication request from a user, the server creates a server card based on information of the user' s card in real time and send it to the user. Different server card is generated for each authentication. Thus, the server card plays a role of one-time password challenge. The user overlaps his/her card with the server card and read an image(eg. a number with four digits) made up from them and inputs the image to the system. This is the authentication process. Keeping security level high, this paper proposes a technique to generate the image clearly and implements it.

• Journal of the Korea Safety Management & Science
• /
• v.13 no.2
• /
• pp.195-202
• /
• 2011

The study focuses on the Repeated Measurements Design (RMD) which observations are periodically made for identical subjects within definite time periods. One of the purposes of this design is to monitor and keep track of replicated records within regular period over years. This paper also presents the classification models of RMD that is developed according to the number of factors in Between-Subject (BS) variates and Within-Subject (WS) variates. The types of models belong to each number of factors: One factor is 0BS 1WS. Two factors are 1BS 1WS and 0BS 2WS. Three factors are 1BS 2WS and 2BS 1WS. Lastly, the four factors include model of 2BS 2WS In addition, the study explains the generation mechanism of models for RMD using Generalizability Design (GD). GD is a useful method for practitioners to identify linear model of experimental design, since it generates a Venn diagram. Lastly, the research develops three types of 1BS 2WS RMDs with crossed factors and nested factors. Those are random models, mixed models and fixed models and they are presented by using Generalizability Design, $(S:A{\times}B){\times}C$. Moreover, the example of applications and its implementation steps of models developed in the study are presented for better comprehension.

• Journal of KIISE:Information Networking
• /
• v.33 no.6
• /
• pp.420-427
• /
• 2006

An RFID system is an important technology that could replace the traditional bar code system changing the paradigm of manufacturing, distribution, and service industry. An RFID reader can recognize several hundred tags in one second. Tag identification is done by tags' random transmission of their IDs in a frame which is assigned by the reader at each round. To minimize tag identification time, optimal frame size should be selected according to the number of tags. This paper presents new query optimization methods in RFID systems. Query optimization consists of tag number estimation problem and frame length determination problem. We propose a simple yet efficient tag estimation method and calculate optimal frame lengths that minimize overall query time. We conducted rigorous performance studies. Performance results show that the new tag number estimation technique is more accurate than previous methods. We also observe that a simple greedy method is as efficient as the optimal method in minimizing the query time.

• Communications for Statistical Applications and Methods
• /
• v.15 no.4
• /
• pp.563-585
• /
• 2008

This paper presents how to improve the efficiency and accuracy in the pricing and sensitivity evaluation for derivatives, since the need for the evaluation of complicated derivatives is increased. The Monte Carlo(MC) simulation using the quasi random number instead of pseudo random number can improve the elapsed time and accuracy for the valuation of European-type derivatives. However, the quasi MC simulation method has its limit for applying it in the multi-dimensional case such as American-type and path-dependent options due to the increased correlation between dimensions as the dimension of random numbers is increased. In order to complement this problem, we develop a modified method in which correlation values are controlled to be below a pre-specified value. Thus, this method is applicable for the pricing of either derivatives ill which underlying assets or risk factors are several or derivatives having path-dependent or early redemption property. Furthermore, we illustrate that it is important to take an appropriate grid interval for the use of finite difference method(FDM) by applying the FDM to one example of non-symmetrical butterfly spreads.