• Journal of the Korea Computer Industry Society
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• v.5 no.5
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• pp.721-728
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• 2004

OCSP (Online Certificate Status Protocol) server which checks the certificate status provides the real time status verification in the PKI (Public Key Infrastructure) system which is the essential system of certificate. However, OCSP server need the message authentication with the server and client, so it has some shortcomings that has slow response time for the demands of many clients concurrently and has complexity of the mathematical process in the public encryption system. In this research, simulation model of the certificate status vertification server is constructed of the DEVS (Discrete EVent system Specification) formalism. This sever model is constructed to practice the authentication with hash function when certificate is checked. Simulation results shows the results of increase of the certificate status verification speed and decrease of the response time to the client.

• KIISE Transactions on Computing Practices
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• v.21 no.1
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• pp.70-75
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• 2015

In this paper, we explore the efficient processing of continuous range queries over a huge number of moving objects, each of which retrieves the moving objects that are currently located within a geographic query region of interest. The moving objects should continually communicate with the server to report their current locations, so as to keep the results of the continuous range queries up-to-date. However, this increases the server workload and involves a enormous amount of communication as the number of continuous range queries and the moving objects becomes enormous. In this paper, we adopt an approach where we leverage available memory and computational resources of the moving objects in order to resolve these problems. To this end, we propose a query indexing structure, referred to as the Space Partitioning Query Index(SPQI), which enables the server to efficiently cooperate with the moving objects for processing continuous range queries. SPQI improves system performance in terms of server workload and communication cost. Through simulations, we show the superiority of SPQI.

• Journal of the Korea Society of Computer and Information
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• v.17 no.6
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• pp.145-152
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• 2012

Due to the large sizes of streaming media, previous delivery techniques are not providing optimal performance. For this purpose, video proxy server is employed for reducing the bandwidth consumption, network congestion, and network traffic. This paper proposes a fast distributed network file system using state transition model in the media streaming system for efficient utilization of video proxy server. The proposed method is composed of three steps: step 1. Training process using state transition model, step 2. base and decision probability generation, and step 3. storing and deletion based on probability. In addition, storage space of video proxy server is divided into each segment area in order to store the segments efficiently and to avoid the fragmentation. The simulation results show that the proposed method performs better than other methods in terms of hit rate and number of deletion. Therefore, the proposed method provides the lowest user start-up latency and the highest bandwidth saving significantly.

• Journal of the Korean Institute of Intelligent Systems
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• v.15 no.5
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• pp.649-654
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• 2005

In this paper, we describe an implementation of real-time face recognition system under ubiquitous computing environments. First, face image is captured by PDA with CMOS camera and then this image with user n and name is transmitted via WLAN(Wireless LAN) to the server and finally PDA receives verification result from the server The proposed system consists of server and client parts. Server uses PCA and LDA algorithm which calculates eigenvector and eigenvalue matrices using the face images from the PDA at enrollment process. And then, it sends recognition result using Euclidean distance at verification process. Here, captured image is first compressed by the wave- let transform and sent as JPG format for real-time processing. Implemented system makes an improvement of the speed and performance by comparing Euclidean distance with previously calculated eigenvector and eignevalue matrices in the learning process.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.10
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• pp.1311-1319
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• 2019

Currently, the web environment is a commonly used area for sharing information and conducting business. It is becoming an attack point for external hacking targeting on personal information leakage or system failure. Conventional signature-based detection is used in cyber threat but signature-based detection has a limitation that it is difficult to detect the pattern when it is changed like polymorphism. In particular, injection attack is known to the most critical security risks based on web vulnerabilities and various variants are possible at any time. In this paper, we propose a novelty detection technique to detect abnormal state that deviates from the normal state on web-server log dataset(WSLD). The proposed method is a machine learning-based technique to detect a minor anomalous data that tends to be different from a large number of normal data after replacing strings in web-server log dataset with vectors using machine learning-based embedding algorithm.

• Journal of the Korea Society of Computer and Information
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• v.25 no.12
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• pp.119-126
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• 2020

In this paper, we design and implement a product information guidance system Based on BLE beacons. This system is designed to provide various functions such as contactless entrance service through mobile ticket, seat guidance service, event push service, content push service, and public service. This system consists of three modules: a beacon recognition module, a server linkage module, and a content transmission module. The beacon recognition module implements a function of transmitting a specific ID of a nearby beacon when a customer with a smartphone approaches the available service area. The server linkage module recognizes the beacon ID value, transfers it to the server, and implements the function to check the location of the server having the ID. The content transmission module implements a function of transmitting event or service information set at a corresponding location to a smartphone. The beacon-based product information guidance system implemented in this paper has the advantage of being able to quickly and easily implement various product information guidance systems.

• Proceedings of the Korea Contents Association Conference
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• 2014.11a
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• pp.25-26
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• 2014

스마트폰의 폭 넓은 보급으로 인해 스마트폰 시장은 급격한 성장을 이루었고, 모바일 환경의 발전은 다양한 형태의 애플리케이션의 개발과 모바일 게임 시장의 성장으로 이어졌다. 모바일 게임에서 사용자간 상호작용은 중요한 요소가 되었다. 하지만 대부분의 모바일 게임들은 소셜네트워크상의 초대와 아이템의 제공, 스코어 비교 등에 그치는 등 제한된 영역에서의 상호작용에 그치는 경향이 있다. 이에 본 논문에서는 메시지 서버를 활용하여 다수의 모바일 디바이스를 유기적으로 연계, 모바일 디바이스의 화면이나 기능을 확장하고 게임세계와 현실세계의 접목을 통한 새로운 형태의 게임 가능성에 대해 연구하였다.

• Information and Communications Magazine
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• v.32 no.10
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• pp.65-70
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• 2015

클라우드 컴퓨팅은 IT 자원(스토리지, 서버, 소프트웨어, 네트워크 등)을 인터넷 기술을 이용하여 서비스 형태로 제공하는 기술이다. 최근 클라우드 컴퓨팅 서비스의 영역이 지속적으로 확대되고 있으며 특히 사물인터넷 (Internet of Things) 등의 IT 기술 발전에 따라 가정, 의료 등에 클라우드 컴퓨팅을 접목하여 활용할 수 있는 방법이 활발히 연구되고 있다. 그러나 클라우드 컴퓨팅 서비스의 확산과 더불어 알려지지 않은 새로운 보안 위협, 클라우드 서비스 고객의 자기정보 통제권 상실, 개인정보 유출로 인해 발생하는 프라이버시 침해 또한 이슈가 되고 있다. 본 논문에서는 클라우드 보안을 위한 국제 표준화 기구와 해당 기구에서 추진 중인 국제 표준화 현황에 대해 살펴본다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.836-838
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• 2003

이 논문에서는 SCORM을 지원하는 교육용 컨텐츠 저작 시스템을 설계하고 구현하였다. 이 시스템은 영역 모델, 항해 모델, 추상인터페이스 모델, 애셋 모델 등 4개의 모델로 구성하였으며, 컨텐츠의 구성을 다이어그램으로 표현할 수 있는 표기법을 지원한다. 이 시스템은 저작 모듈과 실행 모듈로 구성되어 있으며, 저작 모들에서 생성된 각 명세서는 국제적인 교육용 컨텐츠 표준인 ADL SCORM XML 코드를 자동으로 생성하고 실행 모듈과 웹 서버를 통해 서비스된다.

• The KIPS Transactions:PartC
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• v.18C no.2
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• pp.89-96
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• 2011

ASR is an excellent program security technique that protects various data memory areas without run-time overhead. ASR hides the addresses of variables from attackers by reordering variables within a data memory area; however, it can be broken by brute force attacks because of a limited data memory space. In this paper, we propose Multiple ASR to overcome the limitation of previous ASR approaches. Multiple ASR separates a data memory area into original and duplicated areas, and compares variables in each memory area to detect an attack. In original and duplicated data memory areas variables are arranged in the opposite order. This makes it impossible to overwrite the same variables in the different data areas in a single attack. Although programs with Multiple ASR show a relatively high run-time overhead due to duplicated execution, programs with many I/O operations such as web servers, a favorite attack target, show 40~50% overhead. In this paper we develop and test a tool that transforms a program into one with Multiple ASR applied.