• Proceedings of the Korean Information Science Society Conference
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• 2001.10a
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• pp.160-162
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• 2001

최근들어 모바일 환경에서 네트워크 자원을 효율적으로 이용하기 위한 에이전트 기술에 대한 연구가 활발치 진행되고 있으며 이미 많은 분야에서 모바일 에이전트 기술이 사용되고 있다. 그러나, 전자상거래와 같이 데이터 베이스 기능이 필수적인 분야에는 응용에 적합한 데이터베이스 프레임워크가 부족한 실정이다. 본 논문에서는 모바일 환경의 특성인 잦은 접속 해제, 부족한 배터리 용량, 낮은 통신 대역폭, 작은 저장공간 등과 같은 문제 기인한 데이터베이스 어플리케이션의 문제점을 알아보고, 이러한 단점으로 인해 발생되는 모바일 데이터베이스의 트랜잭션 문제의 해결책을 제안한다. Proxync는 분산 환경에서 유용한 프록시(Proxy)를 기반으로 하는 무선 데이터베이스 시스템으로 무선 데이터 동기화를 위해 SyncML이라는 언어를 사용한다. 프록시의 데이터 케쉬 기능을 이용해서 모바일 디바이스의 저장공간 문제를 해결하고 SyncML을 이용해서 접속이 끊어질 때 생길 수 있는 트랜잭션 문제를 해결 할 수 있도록 하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.11a
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• pp.914-917
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• 2012

클라우드 스토리지는 사용자의 요구 또는 데이터의 이용 추이에 따라 자원의 분배를 탄력적으로 제공함으로써 컴퓨팅 자원에 대한 효율적으로 관리가 가능하다. 이에 최근 다양한 서비스가 클라우드 스토리지를 제공하고 있으나, 개인적인 데이터를 소유자가 직접 관리하기 어려워 데이터의 보안성을 보장할 수 없다. 따라서 본 논문에서는 클라우드 스토리지에 저장되는 데이터에 대하여 소유자만이 복호화가 가능하도록 프록시 재암호화를 이용하여 키를 분배하고 데이터를 관리하는 기법을 제안한다. 이를 통해 데이터의 보안성 및 제 3자에 의한 유출을 차단할 수 있다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.10 no.2
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• pp.67-78
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• 2000

인터넷의 급속한 발전으로 학교나 기업체 등의 네트워크가 인터넷을 통해 공유되면서 누구에게나 접속이 허용되어 많은 보안상의 문제가 발생하게 되었다 이러한 문제점을 해결하기 위해서 기존의 호스트 기반 보안 정책에서 네트워크 기반의 보안 시스템으로 침입차단 시스템을 설치하지만 침입차단 시스템은 보안을 위하여 최소 권한만을 인정하므로 사용자에게 투명한 서비스를 제공해주지 못한다. 따라서 본 논문에서는 침입차단 시스템에 프록시를 두어서 서비스의 투명성을 제공하고 강력한 보안 기능을 갖는 FTP 프록시 보안모델(FTP-PSM : FTP Proxy Security Model)을 설계 및 구현을 하고 원격 보안 탐색 도구인 SAINT를 이용하여 FTP-PSM의 안전에 대한취약성 여부를 분석하고 보안기능과 성능과의 관계를 응답시간 측정을 통해 측정함으로써 평가하였다 FTP-PSM은 강한 인증 기능을 위하여 일회용패스워드기능을 제공하고 정당한 사용자에게 서비스 제공여부를 결정하기 위해 강제적 접근제어와 임의적 접근제어 기능 그리고 FTP 명령어 사용 권한을 사용자 그룹별로 인증하는 기능을 제공하여 FTP 보안의 문제점을 해결한다.

• The KIPS Transactions:PartB
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• v.9B no.3
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• pp.303-310
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• 2002

In this paper, we propose a proxy caching scheme that stores a portion of a continuous media object or an entire object on the Internet. The proxy stores the initial fraction of a continuous media object and determines the optimal size of the initial fraction of the continuous media object to be cached based on the object popularity. Under the proposed scheme, the initial latency of most clients and the data transferred from a remote server can be reduced and limited cache storage space can be utilized efficiently. Considering the characteristics of continuous media, we also propose the novel popularity for the continuous media objects based on the amount of the data of each object played by the clients. Finally, we have performed trace-driven simulations to evaluate our caching scheme and the popularity for the continuous media objects. Through these simulations, we have verified that our caching scheme, PPC outperforms other well-known caching schemes in terms of BHR, DSR and replacement and that popularity for the continuous media objects based on the amount of the playback data can enhance the performance of caching scheme.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2785-2792
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• 2011

Such problems as delay, congestion, and crosstalk in the proxy system degrade not only QoS (Quality of Service) but responsiveness and reliability of the streaming media service. To solve this problem this paper proposed a FRTP (Fuzzy Relevance-based Transcoding Proxy) mechanism. The proposed FRTP mechanism analyzes fuzzy similarity for partitioned segment versions of media objects to create a FRTG (Fuzzy Relevance-based Transcoding Graph). Created FRTG determines the transcoding for partitioned media object segment versions. Determined transcoding improves DSR (Delay Saving Ratios), CHPR (Cache Hit Precision Ratio), and CHRR (Cache Hit Recall Ratio). The proposed mechanism is simulated to evaluate such performance parameters as DSR, CHPR, and CHRR. Simulation results shows that the proposed mechanism outperforms in DSR, CHPR and CHRR compared with the other existing mechanisms.

• Journal of Astronomy and Space Sciences
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• v.25 no.4
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• pp.395-404
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• 2008

We explore the linkage between the long term variability of the Sun and earth's climate change by analysing periodicities of time series of solar proxies and global temperature anomalies. We apply the power spectral estimation method named as the periodgram to solar proxies and global temperature anomalies. We also decompose global temperature anomalies and reconstructed total solar irradiance into each local variability components by applying the EMD (Empirical Mode Decomposition) and MODWT MRA (Maximal Overlap Discrete Wavelet Multi Resolution Analysis). Powers for solar proxies at low frequencies are lower than those of high frequencies. On the other hand, powers for temperature anomalies show the other way. We fail to decompose components which having lager than 40 year variabilities from EMD, but both residuals are well decomposed respectively. We determine solar induced components from the time series of temperature anomalies and obtain 39% solar contribution on the recent global warming. We discuss the climate system can be approximated with the second order differential equation since the climate sensitivity can only determine the output amplitude of the signal.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.4
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• pp.197-202
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• 2017

The remote healthcare monitoring system enables a doctor to diagnose and monitor patient's health problem from a distance. Previous researches have focused on key establishment method between a patient and a particular doctor to solve personal health information disclosure problem in data transmission process. However, when considering a misdiagnosis of doctor, the result of a diagnosis by a many doctors is more reliable. In previous work, in order to select multiple doctors, patient should generate shared key for each chosen doctor and perform many times encryptions. Therefore, in this paper, we propose a secure data transmission protocol for receiving diagnosis from multiple doctors using identity-based proxy re-encryption scheme. In proposed protocol, a patient don't need key management work for session key. Also, monitoring server performs re-encryption process on behalf of patient. So, we can reduce computational burden of patient in previous work.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.6
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• pp.1-6
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• 2014

The IoT (Internet of Things) is considered as a core technology to realize interconnected world. At this, companies composing ICT industry and standard organizations make efforts to accelerate it. IETF CoRE(Constrained RESTful Environment) working group standardized CoAP (Constrained Application Protocol) for the constrained device. CoAP has RESTful architecture and CoAP option is provided to use forward-proxy. The forward-proxy is used to translate protocol and perform requests on behalf of the client. However, communication between Internet based client and LLN(Low-power and Lossy Network) based CoAP server architecture has limitations to deploy real IoT service. In this architecture, problems like response delay, URI assignment and DoS attack can be occurred. To solve these problems, we propose the reverse-proxy based system. We consider both of static IoT and mobility IoT environments. Finally, our proposed system is expected to provide efficient IoT service.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.7
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• pp.399-412
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• 2006

A clustering based wireless internet proxy server with cooperative caching has a problem of minimizing overall performance because some servers become overloaded if client request pattern is Hot-Spot or uneven. We propose a self-learning based adaptive clustering scheme to solve the poor performance problems of the existing clustering in case of Hot-Spot or uneven client request pattern. In the proposed scheme, requests are dynamically redistributed to the other servers if some servers supposed to handle the requests become overloaded. This is done by a self-learning based method based dynamic weight adjustment algorithm so that it can be applied to a situation with even various request pattern or a cluster of hosts with different performance. We performed experiments in a clustering environment with 16 PCs and a load balancer. Experimental results show the 54.62% performance improvement of the proposed schemes compared to the existing schemes.

• The KIPS Transactions:PartC
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• v.19C no.2
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• pp.153-166
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• 2012

Multicast service will be required to be an important form of communication without interruption to the delivery of multicast service in mobile networks increasing MNs. In this paper, we review current status of PMIPv6(Proxy Mobile IPv6) multicast listener support being standardized in the IETF and point out limitations of the current approach and we proposed a fast multicast handover procedure in inter domain PMIPv6 network of network-based mobility management. The proposed Fast multicast handover procedure in inter domain optimizes multicast management by using the context of the MNs. We evaluate the proposed fast multicast handover procedure compared to the based one through the developed analytical models and confirm that introduced fast multicast handover procedure provides the reduced service interruption time and total network overhead compared to the based one during handovers.