• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1859-1862
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• 2002

The replication of data is used to increase its availability, improve the performance of a system, and advance the fault-tolerance of a system. In this paper, it is required for the information about the location of a primary site of the replicas of each data item. The replicas of each data item are hierarchically organized to a tree based on the fact that the root is the primary replica in partially replicated databases. It eliminates useless propagation since the propagation can be done to only sites having replicas following the hierarchy of data. And our algorithm schedules transactions so that the execution order of updates at each primary site is identical at all sites by using timestamp. Using our algorithm, the consistent data are supplied and the performance of read-only transactions can be improved by using tree structure of replicas of each data item.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4C
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• pp.290-296
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• 2012

In this paper, we propose a practical authentication system based on Wireless Body Area Networks(WBAN) for U-healthcare medical information environments. The proposed authentication system is based on symmetric cryptosystem such as AES and is designed to not only provide security such as data secrecy, data authentication, data integrity, but also prevent replay attack by adopting timestamp technique and perform secure authentication between sensor node, master node, base-station, and medical server.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2015.11a
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• pp.118-120
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• 2015

본 논문에서는 IP 망을 통한 다윈 스트리밍 미디어 전송 서비스에서 압축된 미디어를 RTP 패킷화하여 전송할 때 RTP 패킷의 헤더에 기록될 타임스탬프 (timestamp) 정보로부터 유도해 낼 수 있는 Normal Play Time 정보를 활용하여 비디오와 오디오 간에 미디어 동기화 지원 방법을 제안한다. 모의실험을 통해 제안된 미디어 동기화 알고리듬을 적용함으로써 서로 다른 미디어 간에 정확한 동기화가 제공됨을 확인할 수 있었다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04b
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• pp.55-57
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• 2004

이동 컴퓨팅(Mo띠le Computing) 환경에서 빈번한 접속 단절은 클라이언트의 캐시 일관성(Consistency) 문제로 직결된다. 본 논문에서는 이를 해결하기 일한 무효화 보고(Invalidation Report. In)중 하나를 제시한다. 기존의 IR방식은 대량의 데이터와 빈번한 데이터의 갱신(Update)시 IR 길이의 증기폭이 상당히 크다. 이는 타임스탬프가 IR에서 차지하는 비중이 큼으로써 오는 현상이다. 또한 기존방식은 캐시 레벨의 선택적 청취(Selective tuning)를 지원하지 못하는 문제점을 가지오 있다. 이러한 점을 극복하고자 B＋Tree를 기반으로 시간 값을 구성하고 이에 따른 데이터 아이디를 재구성하는 IR방식을 제안한다. 이를 활용하면 각 클라이언트가 자신의 단절(Disconnect)된 시간에 맞는 갱신 정보를 확인할 수 있게 된다. 이러한 방법은 기존 IR의 단점을 보완하며 선택적 청취론 유도할 수 있는 효과적인 방법이다.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.04a
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• pp.115-118
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• 2014

트랜잭셔널 메모리는 다중 코어 시스템에서 lock 을 대체할 메모리 동기화 기법으로 소개되었다. 트랜잭셔널 메모리를 사용하는 시스템에서 같은 주소의 메모리에 동시에 접근하여 충돌이 일어난 트랜잭션은 충돌해결정책에 의해 유효화 될지 버려질지 선택된다. 기존의 트랜잭셔널 메모리는 고정된 충돌해결정책을 사용하여, 상황에 따라 가장 유리한 트랜잭션을 선택 해주지 못하는 한계가 있었다. 본 논문에서는 상황에 따라 여러 정책 중 유리한 충돌해결정책을 판단하여 적용시키는 방법을 제안한다. STAMP 벤치마크를 통한 시뮬레이션 결과, 제안하는 방법은 기존에 사용되는 Timestamp, Karma 충돌해결정책 대비 평균 22% 높은 성능 향상을 보였다.

• International journal of advanced smart convergence
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• v.10 no.2
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• pp.10-14
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• 2021

Today people adopt various contents from their mobile devices which lead to numerous platforms. As technology of 5G, IOT, and smart phone develops, the number of people who create, edit, collect, and share their own videos, photos, and articles continues to increase. As more contents are shared online, the numbers of data being stolen continue to increase too. To prevent these cases, an authentication method is needed to encrypt the content and prove it as its own content. In the report, we propose a few methods to secure various misused content with secondary security. A unique private key is designed when people create new contents through sending photos or videos to platforms. The primary security is to encrypt the "Private Key" with a public key algorithm, making its data-specific "Timeset" that doesn't allow third-party users to enter. For the secondary security, we propose to use Message Authentication Codes(MACs) to certify that we have produced the content.

• Journal of Multimedia Information System
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• v.8 no.4
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• pp.243-250
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• 2021

Instructional contents are used to demonstrate a technical process to teach and walkthrough certain procedures to carry out a task. This type of informational content is widely used for teaching and lectures in form of tutorial videos and training videos. Since there are questions and uncertainties for what could be the killer application for the novel wearables, we propose a self-instruction training application on a smart glass to utilize already-available instruction videos as well as public open data in creative ways. We design and implement a prototype application to help users train by wearing smart glasses specifically designed for two concrete and hand-constrained use cases where the user's hands need to be free to operate. To increase the efficiency and feasibility of the self-instruction training, we contribute to the development of a wearable killer application by integrating a voice-based user interface using speech recognizer, public open data APIs, and timestamp-based procedural content navigation structure into our proof-of-concept application.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.4
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• pp.340-349
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• 2017

This paper is proposed Hadoop security protocol to protect a reply attack and impersonation attack. The proposed hadoop security protocol is consists of user authentication module, public key based data node authentication module, name node authentication module, and data node authentication module. The user authentication module is issued the temporary access ID from TGS after verifing user's identification on Authentication Server. The public key based data node authentication module generates secret key between name node and data node, and generates OTKL(One-Time Key List) using Hash-chain. The name node authentication module verifies user's identification using user's temporary access ID, and issues DT(Delegation Token) and BAT(Block Access Token) to user. The data node authentication module sends the encrypted data block to user after verifing user's identification using OwerID of BAT. Therefore the proposed hadoop security protocol dose not only prepare the exposure of data node's secret key by using OTKL, timestamp, owerID but also detect the reply attack and impersonation attack. Also, it enhances the data access of data node, and enforces data security by sending the encrypted data.

• The KIPS Transactions:PartC
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• v.11C no.3
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• pp.379-386
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• 2004

The WAP 2.0 system is a newly proposed wireless communication system by the WAP Forum for interoperability across Internet environment and the system takes charge of communication between WAP terminals and existing origin Web servers. The purpose of this paper is 1) to construct a WAP 2.0 proxy proposed by the WAP Forum and 2) to improve the WAP Proxy in order to increase communication efficiency between wired and wireless communication objects. The Improved WAP proxy constructed in this study provides links between wired and wireless communication environments using the split-TCP concept. However, unlike the split-TCP connection, The improved WAP proxy maintains TCP's end-to-end semantics and reduces overhead by avoiding operations as much as possible on the upper protocol layer. In addition, The improved WAP proxy supports SACK(Selective Acknowledgement ) option and Timestamp option for speedy re-transmission which leads to reduction of performance degradation. After constructing the improved WAP proxy under Linux environment, experiments have been taken. The experimental results show that, compared with the experiments when a WAP proxy proposed by the WAP Forum is used, both data transmission delay time and data transmission size decrease to show that communication efficiency is increased. In particular, as packet missing ratio Increases, data transmission size decreases, which demonstrates that the improved WAP proxy is very effective for performance improvement in wireless communication environment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.3 no.5
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• pp.527-547
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• 2009

Moving object management is widely used in traffic, logistic and data mining applications in ubiquitous environments. It is required to analyze spatio-temporal data and trajectories for moving object management. In this paper, we proposed a novel index structure for spatio-temporal aggregation of trajectory in a constrained network, named aCN-RB-tree. It manages aggregation values of trajectories using a constraint network-based index and it also supports direction of trajectory. An aCN-RB-tree consists of an aR-tree in its center and an extended B-tree. In this structure, an aR-tree is similar to a Min/Max R-tree, which stores the child nodes' max aggregation value in the parent node. Also, the proposed index structure is based on a constrained network structure such as a FNR-tree, so that it can decrease the dead space of index nodes. Each leaf node of an aR-tree has an extended B-tree which can store timestamp-based aggregation values. As it considers the direction of trajectory, the extended B-tree has a structure with direction. So this kind of aCN-RB-tree index can support efficient search for trajectory and traffic zone. The aCN-RB-tree can find a moving object trajectory in a given time interval efficiently. It can support traffic management systems and mining systems in ubiquitous environments.