• Proceedings of the Korea Multimedia Society Conference
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• 2003.11a
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• pp.150-153
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• 2003

지속적으로 증가하고 있는 웹사이트는 사용자마다 유일한 신분확인정보(ID, 패스워드)를 요구 한다. 이 때 사용자는 웹사이트마다 별개의 계정을 만드는 것이 공격자의 위협으로부터 안전하지만, 현실적으로 사용자의 기억의 한계, 편의 추구로 인해 한 사용자가 사용하는 계정의 가짓수는 한정되기 마련이다. 따라서, 어느 공격자가 단일 사용자의 특정 웹사이트에 대한 ID와 패스워드를 알게되면, 기공격자는 다른 웹사이트에 동일한 ID와 패스워드를 사용한 로그인 시도 공격이 성공할 확률이 매우 높다고 할 수 있다. 본 논문에서는 이러한 사용자 ID와 패스워드에 대한 문제점을 해결하기 위한 방안으로서 사용자는 로그인하려는 웹사이트에 상관없이 항상 동일한 ID와 패스워드를 사용하지만, 실질적으로는 사용자 머신내에 있는 내부 프록시(proxy)에 의해서 웹사이트마다 독립적이고 유일한 가명ID와 가명 패스워드를 생성하는 방안을 제안한다. 또한 제안 방안에서는 임계 암호 기법을 이용하여 단일 사용자 ID와 패스워드로부터 가명 ID와 가명 패스워드를 생성하는 함수를 안전하게 구성한다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.649-651
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• 2005

본 논문에서는 실제 모바일 환경에서의 멀티미디어 컨텐츠의 요청 패턴을 분석하고 그 결과를 반영한 캐싱 알고리즘을 제안한다. 로그 데이터를 분석한 결과 컨텐츠의 연속적인 요청이 매우 짧은 시간 동안 이루어지는 시간적인 특성을 발견했으며, 컨텐츠의 다른 버전 사이의 요청 시간이 짧음을 통해서 버전별 컨텐츠의 요청이 응집되어 나타남을 확인했다. 제안된 알고리즘에서는 시간적인 특성과 컨텐츠의 인기도 특성을 반영하기 위해 측정 시간 윈도우 내에서 컨텐츠의 요청 횟수를 측정하고, 요청 횟수의 임계값 이상의 컨텐츠에 대해서 유지 시간 단위만큼의 컨텐츠 만료 시간을 정한다. 또한 공간적인 특성을 이용하여 컨텐츠가 캐시에서 제거될 때, 만료시간이 지난 컨텐츠의 다른 버전을 동시에 캐시에서 제거하는 방법을 사용한다 실험 결과 캐시의 크기가 작은 경우 제안된 알고리즘이 기존 알고리즘에 비해 $1-5\%$ 정도 성능향상을 보였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.6
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• pp.229-240
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• 2012

The development of multimedia applications followed by development of high-speed networks has improved the performance of mobile devices with high transfer speed broadband. Mobile internet access has made possible seamless indoor and outdoor mobile multicast services. Multicasting services are used to support efficient group communications. However, mobile multicasting services have two constraints: tunnel convergence and handover latency. Many protocols and handover methods have been proposed to address these problems. The inter-LMA optimized handover model for multicasting services has previously been proposed for PMIPv6-based networks. The proposed model removes the tunnel convergence issue and reduces router processing costs. It also makes possible the performance of fast handover operations with adaptive transmission mechanisms. In addition, the proposed scheme exhibits low packet delivery costs and handover latency in comparison with existing schemes, and ensures fast handover when moving the inter-LMA domain

• The KIPS Transactions:PartA
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• v.16A no.3
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• pp.181-188
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• 2009

Transcoding is one of core techniques that implement VoD services according to QoS. But it consumes a lot of CPU resource. A transcoding proxy transcodes multimedia objects to meet requirements of various mobile devices and caches them to reuse later. In this paper, we propose a service policy that reduces the load of transcoding multimedia objects by degrading QoS in a transcoding proxy. Due to the tradeoff between QoS and the load of a proxy system, a transcoding proxy provides lower QoS than a client's requirement so that it can accomodate more clients.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.3
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• pp.258-267
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• 2013

Recently, Proxy Mobile IPv6(PMIPv6) networks have been drawing attention as the mobility management protocol that uses limited wireless resources effectively. And the multicast, which is a core technology of the Internet broadcast system such as mobile IPTV, has been widely discussed mainly based on PMIPv6 network. However, PMIPv6-based multicast cannot support the global mobility directly between different PMIPv6 domains because PMIPv6 is basically designed for local mobility in single PMIPv6 domain. Moreover, PMIPv6-based multicast causes the disconnection of services because it does not solve the packet loss problem during binding and group joining procedure. In this paper, we propose a global mobility scheme that supports the seamless multicast service in PMIPv6 networks. The proposed scheme supports the global mobility due to the addition of extra signalling messages between LMAs. Also, it achieves low latency because it performs fast binding and group joining procedure. We present the simulation results which show that the proposed scheme achieves the global mobility with low latency through the NS-2 simulation.

• Journal of Korea Multimedia Society
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• v.7 no.8
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• pp.1066-1077
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• 2004

Dramatic increase in the number of Internet users want highly qualified service of continuous media contents on the web. To solve these problems, we present two network caching schemes(PPC, PPCwP) which consider the characteristics of continuous media objects and user access pattern in this paper. While there are plenty of reasons to create rich media contents, delivering this high bandwidth contents over the internet presents problems such as server overload, network congestion and client-perceived latency. PPC scheme periodically calculates the popularity of objects based on the playback quantity and determines the optimal size of the initial fraction of a continuous media object to be cached in proportion to the calculated popularity. PPCwP scheme calculates the expected popularity using the series information and prefetches the expected initial fraction of newly created continuous media objects. Under the PPCwP scheme, the initial client-perceived latency and the data transferred from a remote server can be reduced and limited cache storage space can be utilized efficiently. Trace-driven simulation have been performed to evaluate the presented caching schemes using the log-files of iMBC. Through these simulations, PPC and PPCwP outperforms LRU and LFU in terms of BHR and DSR.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.11a
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• pp.100-102
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• 2023

최근 오픈 사이언스 문화가 확산됨에 따라 오픈 데이터, 오픈 소스 소프트웨어와 같은 공개된 리소스들을 효율적으로 공유 및 활용하기 위한 방법이 주목을 받고 있다. 본 논문에서는 연구 소프트웨어의 재현성을 향상시키기 위한 국가연구데이터커먼즈(KRDC)를 소개하고 다중 KRDC 클러스터 간 워크플로우 연계 방안을 제안한다. 국가연구데이터커먼즈는 연구 소프트웨어와 분석 환경인 인프라를 결합하여 함께 제공하는 서비스로, 멀티 노드 쿠버네티스(kubernetes) 클러스터를 기반으로 동작한다. 따라서, 서로 다른 KRDC 프레임워크에 존재하는 리소스들을 하나의 워크플로우로 연계하는 것은 복잡한 사용자 인증/인가 문제, 보안 상의 문제를 고려하여야 한다. 본 논문에서는 프록시(proxy) 앱을 사용하는 워크플로우 연계 기능을 제안하고, 이를 지원하기 위한 통합 인증, 인가 체계와 연계 방안을 구현한다. 제안하는 방법을 두 개의 KRDC 프레임워크를 대상으로 적용하여 제안 워크플로우 연계 방법의 유효함을 확인한다. 본 논문에서 제안하는 워크플로우 연계 방법과 시나리오는 실제 멀티 클러스터 연계 방안을 구현한 사례로, KRDC 프레임워크 뿐만 아니라 다양한 쿠버네티스 기반 리소스 연계에 활용할 수 있는 우수한 결과로 사료된다.

• Journal of KIISE:Information Networking
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• v.37 no.1
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• pp.72-83
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• 2010

Group communication in a wireless mesh network is complicated due to dynamic intermediate mesh points, access control for communications between different administrative domains, and the absence of a centralized network controller. Especially, many-to-many multicasting in a dynamic mesh network can be modeled by a decentralized framework where several subgroup managers control their members independently and coordinate the inter-subgroup communication. In this study, we propose a topology-matching decentralized group key management scheme that allows service providers to update and deliver their group keys to valid members even if the members are located in other network domains. The group keys of multicast services are delivered in a distributed manner using the identity-based encryption scheme. Identity-based encryption facilitates the dynamic changes of the intermediate relaying nodes as well as the group members efficiently. The analysis result indicates that the proposed scheme has the advantages of low rekeying cost and storage overhead for a member and a data relaying node in many-to-many multicast environment. The proposed scheme is best suited to the settings of a large-scale dynamic mesh network where there is no central network controller and lots of service providers control the access to their group communications independently.

• Journal of Internet Computing and Services
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• v.14 no.3
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• pp.67-79
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• 2013

In wireless networks, efficient mobility management to support of mobile users is very important. Several mobility management schemeshave been proposed with the aim of reducing the signaling traffic of MN(Mobile Node). Among them, PMIPv6 (Proxy Mobile IPv6) is similar with host-based mobility management protocols but MN does not require any process for mobility. By introducing new mobile agent like MAG (Mobile Access Gateway) and LMA (Local Mobility Anchor), it provides IP mobility to MN. In this paper, we propose the analytical model to evaluate the mean signalingdelay and the mean bandwidth according to the type of MN mobility. As a result of mathematical analysis, MF-PMIP (Multicasting-based FastPMIP) outperforms compared to F-PMIP and PMIP in terms of parameters for the performance evaluation.

• Journal of Korea Multimedia Society
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• v.7 no.5
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• pp.668-679
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• 2004

When users of mobile environments move fast or slow into a number of base stations(BS) and request the services of continuous media data such as video or audio, this study examines what the caching has the usefulness in mobile environments. Namely, to reduce packet disconnections and network overheads in mobile environments and minimize transmission delay time, we propose domain-based hierarchical caching structure and study whether application of caching has the usefulness. So we have a model based on user environments and hierarchical network structure to process continuous media services, and analyze the usefulness of caching which depends on the mobile patterns of user and the locations of caching nodes. And then, we research whether caching offers the usefulness in mobile environments. As the result, we are able to see that an adaptable application of caching is needed because the hit ratio and the number of replacement vary in large according to mobile patterns of user and locations of caching.