• Proceedings of the IEEK Conference
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• 2000.11c
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• pp.51-54
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• 2000

Due to the emerging of high-speed network, lots of interests of access to remote data have increased. Those interests motivate using of Cooperative Caching that uses remote cache like local cache by sharing other clients' cache. The conventional algorithm like GMS(Global Memory Service) has some disadvantages that occurred bottleneck and decreasing performance because of exchanges of many messages to server or manager. On the other hand, Hint-based algorithm resolves a GMS's server bottleneck as each client has hint information of all blocks. But Hint-based algorithm also causes some problems such as inaccurate information in it, if it has too old hint information. In this paper, we offer the policy that supplement bottleneck and inaccuracy； by using file identifier that can search for the lookup table and by exchanging oldest block information between each client periodically.

• Journal of Digital Convergence
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• v.12 no.10
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• pp.259-264
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• 2014

The web server is configured to display the list of files contained in this directory. This is not recommended because the directory may contain files that are not normally exposed through links on the web site. The directory list have some serious vulnerability to show internal files and directory to outsider attackers. Therefore, the proposed countermeasure of directory list is presented to prevent unnecessary valuable information from outsider attackers.

• The KIPS Transactions:PartC
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• v.9C no.5
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• pp.757-764
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• 2002

This Paper describes our experiences with the design and implementation of a networked multimedia information management system in an object-oriented framework for distributed multimedia applications, and an integrated QoS-resource negotiation protocol which has been applied to a video server in our networked multimedia infrastructure. The salient features of our framework to support efficient multimedia streaming are explained. Next the paper explores the challenges faced in integrating the proposed QoS negotiation policy into the framework.

• Journal of Korea Society of Digital Industry and Information Management
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• v.17 no.2
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• pp.21-28
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• 2021

In this paper, a study on a method for designing and implementing an environmental information system to support environmental activities was done. First of all, research on the similar information system and necessary functions were derived. Necessary functions were largely classified into functions for cooperation such as policy consultation and publicity, and functions for environmental information data. Collaboration functions are classified in detail, and detailed contents of this function are summarized. In addition, a data model was designed for various environmental information, and an information server and client interface are designed as a cloud application. Cloud server configuration and design, and client web and app programs to access these information were implemented and tested each functions successfully.

• Journal of applied mathematics & informatics
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• v.41 no.6
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• pp.1155-1171
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• 2023

This paper investigates a non Markovian M/G/1 queue with retrial policy, different kind of service rates as well as unsatisfied clients which is inspired by an example of a transmission medium access control in wireless communications. The server tends to work continuously until it finds at least one client in the system. The server will begin its maintenance tasks after serving all of the clients and if the system becomes empty. Provisioning periods in regular working periods and maintenance service periods should be evenly divided. Using supplementary variable technique, the amount of clients in the system as well as in the orbit were found. Further few performance measures of the system were demonstrated numerically.

• Journal of Digital Convergence
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• v.12 no.2
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• pp.335-341
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• 2014

To play the networked video contents in a client's mobile device in real time, the contents should be delivered to it by the contents server with streaming technology. Generally, in a server-client based commerce model, the server is in charge of both the authentication of the paid customer and distribution of the contents. The drawback of it is that if the customers' requests go on growing rapidly, the service quality would be degraded results from the problems of overloaded server or restricted network bandwidth. On the contrary, in P2P based networks, more and more the demand for service increasing, the service quality is upgraded since a customer can act as a server. But, in the P2P based network, there are too many servers to manage, it's possible to distribute illegal contents because the P2P protocol cannot control distributed servers. Thus, it's not suitable for commercial purposes. In this paper, the dymanic group authentication scheme is proposed which is suited to P2P based applications. The proposed scheme consists of group based key generation, key update, signature generation and verification protocols. It can control the seeder's state whether the seeder is joining or leaving the network, and it can be applied to hybrid P2P based commerce model where sales transactions are covered by the index server and the contents are distributed by the P2P protocol.

• Journal of Digital Convergence
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• v.15 no.10
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• pp.253-260
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• 2017

Authenticated key agreement in multi-server environments is one of very important security issues because only authorized user needs to access their data and services. To support this issue, numerous schemes have been proposed over recent years. Recently, Shin showed the security weaknesses in the previous scheme and proposed an improved scheme called SIAKAS to solve them. Unfortunately, this paper shows that SIAKAS is still weak against application server impersonation attack and could be traceable to attackers. To solve the problems in SIAKAS, we propose an untraceable authenticated key agreement scheme, denoted by UAKAS. UAKAS efficiently solves security and privacy issues in SIAKAS and the related schemes and could reduce the operation overhead at least 12% compared to them.

• Journal of Digital Convergence
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• v.13 no.9
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• pp.287-295
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• 2015

The IPTV service has to be converted into an unified media format that fits for a variety of terminal equipments in terms of the bulk high-capacity media contents, and is spending a lot of time in the conversion time of contents including the process of collecting the media contents and extracting the information for conversion. In order to solve the problem, this paper designed the database in accordance with the automatic collection of time, and proposed a system that could increase the productivity of the contents through the automation process of the entire process using the media server and the transcoder. The media server collected contents and extracted information automatically with respect to the contents servers placed in specific locations and the media files of the storage whereas the transcoder conducted the automatic upload of the converted results to a specific server through the process of automatic conversion. As a result, the various convergence through compared to existing conversion method could minimized unnecessary waste of time.

• Journal of Digital Convergence
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• v.17 no.12
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• pp.235-241
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• 2019

The structure of the IoT can be divided into devices, gateways, and servers. First, the gateway collects data from the device, and the gateway sends data to the server through HTTP protocol, Websocket protocol, and MQTT protocol. The processing server then processes, analyzes, and transforms the data, and the database makes it easy to store and use this data. These IoT services are basically centralized structures with servers, so attacks on the entire platform are concentrated only on the central server, which makes hacking more successful than distributed structures. One way to solve this problem is to develop IoT that combines blockchain. Therefore, the proposed research suggests that the blockchain is a distributed structure, in which blocks containing small data are connected in a chain form, so that each node agrees and verifies the data with each other, thereby increasing reliability and lowering the probability of data forgery.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.571-574
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• 2005

XCAP(XML Configuration Access Protocol) which has been proposed in IETF is based on both XML and HTTP protocol. XCAP server maintains user's configuration information for specific application which is described by XML. This protocol can be applied to many application servers for adapting user's preferences. There can be many way to interwork with other application servers. In this paper, we will talk about the experience of designing and implementation of XCAP server and the way of interwork with application servers.