• Proceedings of the Korean Information Science Society Conference
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• 1999.10a
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• pp.60-62
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• 1999

SGML이나 XML과 같은 마크업 언어를 사용하여 생성된 구조적 문서에 대한 검색 시스템은 문서의 임의의 부분에 대한 검색을 지원한다. 문서의 구조에 바탕을 둔 다양한 유형의 사용자 질의를 처리하기 위해서는 색인에 필요한 메모리량이 커지게 된다. 색인에 필요한 메모리양을 줄이기 위해, 색인된 노드의 ID에서 찾고자 하는 노드의 ID를 계산할 수 있어야 한다. 그러나 이 경우 각 노드에 ID가 고정되기 때문에 문서의 갱신이 발생할 때 많은 부분이 수정되어야 하기 때문에 갱신에 필요한 오버헤드가 커지게 된다. 본 논문에서는 전체문서인스턴스트리 구조를 제안하고, 이를 기반으로 하여 노드의 ID를 구성함으로서, 색인과 검색의 효율성을 유지하면서 자료의 추가나 삭제등의 갱신이 발생할 때, 갱신의 파장을 최소화시킬 수 있는 색인구조와 질의처리 알고리즘을 제시한다.

• The KIPS Transactions:PartC
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• v.10C no.2
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• pp.217-232
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• 2003

QoS routing can improve network performance while providing support for QoS guarantees. These benefits, however, comes with additional routing costs such as more complex and frequent route computation and the protocol overheads to exchange dynamic network state information. Moreover, little has been done to mininize the impact of the QoS traffic to the best effort traffic or to enhance the routine Performance of the best effort traffic when QoS routing is deployed. In this paper, it is proposed that a sewer based routing mechanism, which supports the QoS routing without incurring the QoS routing protocol overhead for the network state update exchanges and enhances the performance of the best effort traffic without affecting the performance of QoS routing. Simulation results show that the proposed scheme enhances the routing performance for the QoS traffic while reducing the routing protocol overhead. The routing performance of the best traffic is also improved with virtually no impact to the routine performance of the QoS traffic. The proposed scheme is shown to be especially effective when the ratio of QoS traffic is high, that is, when the impact of the QoS traffic to the performance of best effort traffic is significant.

• Journal of KIISE:Information Networking
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• v.29 no.6
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• pp.625-634
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• 2002

Cryptography is the methods of making and using secret writing that is necessary to keep messages private between two parties. Cryptography is compute-intensive algorithm and needs cpu resource excessively. To solve these problems, there exists hardware approach that implements cryptographic algorithm with hardware chip. In this paper, we presents the design and implementation of cryptographic hardware and compares its performance with software cryptographic algorithms. The experimental result shows that the hardware approach causes high I/O overheads when it transmits data between cryptographic board and host cpu. Hence, low complexity cryptographic algorithms such as DES does not improve the performance. But high complexity cryptographic algorithms such as Triple DES improve the performance with a high rate, roughly from two times to Sour times.

• Journal of KIISE:Information Networking
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• v.30 no.3
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• pp.329-342
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• 2003

Most of the existing multicast routing protocols for ad-hoc networks do not take into account the efficiency of the protocol for the cases when there are large number of sources in the multicast group, resulting in either large overhead or poor data delivery ratio when the number of sources is large. In this paper, we propose a multicast routing protocol for ad-hoc networks, which particularly considers the scalability of the protocol in terms of the number of sources in the multicast groups. The proposed protocol designates a set of sources as the core sources. Each core source is a root of each tree that reaches all the destinations of the multicast group. The union of these trees constitutes the data delivery mesh, and each of the non-core sources finds the nearest core source in order to delegate its data delivery. For the efficient operation of the proposed protocol, it is important to have an appropriate number of core sources. Having too many of the core sources incurs excessive control and data packet overhead, whereas having too little of them results in a vulnerable and overloaded data delivery mesh. The data delivery mesh is optimally reconfigured through the periodic control message flooding from the core sources, whereas the connectivity of the mesh is maintained by a persistent local mesh recovery mechanism. The simulation results show that the proposed protocol achieves an efficient multicast communication with high data delivery ratio and low communication overhead compared with the other existing multicast routing protocols when there are multiple sources in the multicast group.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.5
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• pp.115-124
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• 2005

We propose a new binding update(BU) protocol between mobile node(CN) and correspondent node(CN) for the purpose of preventing redirect attacks and DoS attacks observed from the existing BU protocols and enhancing the efficiency of the BU protocol. Home agent plays a role of both authentication server validating BU message and session key distribution center for MN and CN. Also propose the stateless Diffie-Hellman key agreement based on cryptographically generated address (CGA). Suity of our proposed Protocol is analyzed and compared with other protocols. The proposed protocol is more efficient than previous schemes in terms of the number of message flows and computation overhead and is secure against both redirect and DoS attacks.

• Convergence Security Journal
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• v.6 no.1
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• pp.83-90
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• 2006

Recently, the security for RFID/USN environment is divided into network security and RFID security. The authentication protocol design for RFID security is studied to protect user privacy in RFID system. However, the study of efficient authentication protocol for RFID system is not satisfy a security for low-cost RFID tag and user privacy. Therefore, this paper proposes a secure matrix-based RFID authentication protocol that decrease communication overhead and computation. In result, the Matrix-based RFID authentication protocol is an effective authentication protocol compare with HB and $HB^+$ in traffic analysis attack and trace location attack.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.05a
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• pp.994-997
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• 2013

가비지 컬렉션(Garbage Collection)은 시스템에서 더 이상 사용하지 않는 동적 할당된 메모리 블록 혹은 개체를 찾아 자동적으로 다시 사용 가능한 자원으로 회수하는 것을 의미한다. 최근 대부분의 프로그래밍 언어에서는 메모리 관리를 자동으로 처리해주는 가비지 컬렉터를 기본적으로 포함하고 있으며 이러한 시스템 환경은 개발자들의 개발 속도 향상과 프로그램 가독성을 높여주는 이점을 주고 있다. 그러나 가비지 컬렉터는 자원이 한정되어 있는 스마트폰과 같은 환경에서는 큰 오버헤드를 가지며 성능 저하의 주 원인으로 꼽히기도 한다. 따라서 iOS의 경우에는 가비지 컬렉터를 지원하지 않는다. 이에 따라 본 연구에서는 스마트폰의 안드로이드와 iOS의 프로그래밍 언어인 Java와 Object C의 가비지 컬렉터의 알고리즘을 분석하여 두 언어의 개발환경의 차이를 비교 하였다. 또한 앞으로 Object C의 메모리 관리 정책에 대하여 서술하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.61-62
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• 2007

본 논문에서는 도로 네트워크 데이터베이스에서 k-최근접 이웃 질의를 효율적으로 처리하기 위한 방안에 대하여 논의한다. 네트워크 거리는 삼각형 부등식 성질(triangular inequality property)을 만족하지 못하므로 기존의 기법들은 네트워크 거리를 기반으로 하는 인덱스를 사용하지 않았다. 이러한 기법들은 질의 처리 시 심각한 성능 저하의 문제를 가진다. 사전 계산된 네트워크 거리를 이용하는 또 다른 기법은 저장 공간의 오버헤드가 크다는 문제를 갖는다. 본 논문에서는 이러한 두 가지 문제점들을 동시에 해결하기 위하여 객체들 간의 네트워크 거리를 근사하여 객체들에 대한 인덱스를 구축하고, 이를 이용하여 k-최근접 이웃 질의를 처리하는 새로운 기법을 제안한다. 실제 도로 네트워크를 이용한 정확도 검증 실험을 통하여 제안된 기법의 우수성을 규명한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.1
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• pp.63-71
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• 2013

In order to support mobility for sink groups, it is important to get the current location of a mobile sink group and then to offer the location to a source. Typically, previous works calculate a region including all member sinks by flooding; then, it notifies this region information to a source. However, flooding and location updates are periodically performed regardless of the group movement so that it causes considerable control overhead. In this paper, we propose an energy-efficient scheme supporting mobile sink groups. The proposed scheme obtains a location of a group without flooding. It exploits the inherent property of mobile sink groups which could approximate entire group movement by only partial member sinks movement. Also, the scheme learns group location by back-propagation learning method through exploiting overhearing feature in wireless communication environment. Our simulation studies show that the proposed scheme significantly improves in terms of energy consumption compared to the previous work.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12B
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• pp.1066-1080
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• 2003

In this paper a scalable QoS routing scheme for distributed multimedia applications in a hierarchical wide area network is proposed. The problem of QoS routing is formulated as a multicriteria shortest path problem, known as NP-complete. The proposed hierarchical routing scheme consists of two phases. In Phase 1, every border node periodically pre-computes the QoS distance for the paths between every pair of border nodes in any level of domain hierarchy. This phase is independet of the QoS request from an application. In Phase II, distributed graph construction algorithm is performed to model the network as a graph by retrieving pre-computed QoS distances. The graph is constructed by the on-demand algorithm and contains a part of the network topology which is completely neglected or partially considered by existing routing schemes, thus maintaining more accurate topology information. By using retrieval approach rather than advertising one, no global QoS state information exchange among nodes is needed. In this Phase, distributed partition algorithm for QoS routing problem is also performed, thus eliminating virtual links on the hierarchically complete path.