• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.2
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• pp.417-429
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• 2019

WPA2-PSK uses a 4-way handshake protocol based on a shared secret to establish a secure session between a client and an AP. It has various security problems such as eavesdropping attacks and the secure session establishment process is inefficient because it requires multiple interactions between client and AP. The WPA3 standard has recently been proposed to solve the security problem of WPA2, but it is a small improvement using the same 4-way handshake methodology. OAuth 2.0 token authentication is widely used on the web, which can be used to keep an authenticated state of a client for a long time by using tokens issued to an authenticated client. In this paper, we apply the dual-token based randomized token authentication technology to the Wi-Fi security protocol to achieve an efficient Wi-Fi security protocol by dividing initial authentication and secure session establishment. Once a client is authenticated and equipped with dual tokens issued by AP, it can establish secure session using them quickly with one message exchange over a non-secure channel.

• Journal of Audiology & Otology
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• v.25 no.1
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• pp.14-21
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• 2021

Background and Objectives: There is growing interest in the use of the Level-specific (LS) CE-Chirp^® stimulus in auditory brainstem response (ABR) due to its ability to produce prominent ABR waves with robust amplitudes. There are no known studies that investigate the test-retest reliability of the ABR to the LS CE-Chirp^® stimulus. The present study aims to investigate the test-retest reliability of the ABR to the LS CE-Chirp^® stimulus and compare its reliability with the ABR to standard click stimulus at multiple intensity levels in normal-hearing adults. Subjects and Methods: Eleven normal-hearing adults participated. The ABR test was repeated twice in the same clinical session and conducted again in another session. The ABR was acquired using both the click and LS CE-Chirp^® stimuli at 4 presentation levels (80, 60, 40, and 20 dBnHL). Only the right ear was tested using the ipsilateral electrode montage. The reliability of the ABR findings (amplitudes and latencies) to the click and LS CE-Chirp^® stimuli within the same clinical session and between the two clinical sessions was calculated using an intra-class correlation coefficient analysis (ICC). Results: The results showed a significant correlation of the ABR findings (amplitude and latencies) to both stimuli within the same session and between the clinical sessions. The ICC values ranged from moderate to excellent. Conclusions: The ABR results from both the LS CE-Chirp^® and click stimuli were consistent and reliable over the two clinical sessions suggesting that both stimuli can be used for neurological diagnoses with the same reliability.

• Korean Journal of Audiology
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• v.25 no.1
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• pp.14-21
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• 2021

Background and Objectives: There is growing interest in the use of the Level-specific (LS) CE-Chirp^® stimulus in auditory brainstem response (ABR) due to its ability to produce prominent ABR waves with robust amplitudes. There are no known studies that investigate the test-retest reliability of the ABR to the LS CE-Chirp^® stimulus. The present study aims to investigate the test-retest reliability of the ABR to the LS CE-Chirp^® stimulus and compare its reliability with the ABR to standard click stimulus at multiple intensity levels in normal-hearing adults. Subjects and Methods: Eleven normal-hearing adults participated. The ABR test was repeated twice in the same clinical session and conducted again in another session. The ABR was acquired using both the click and LS CE-Chirp^® stimuli at 4 presentation levels (80, 60, 40, and 20 dBnHL). Only the right ear was tested using the ipsilateral electrode montage. The reliability of the ABR findings (amplitudes and latencies) to the click and LS CE-Chirp^® stimuli within the same clinical session and between the two clinical sessions was calculated using an intra-class correlation coefficient analysis (ICC). Results: The results showed a significant correlation of the ABR findings (amplitude and latencies) to both stimuli within the same session and between the clinical sessions. The ICC values ranged from moderate to excellent. Conclusions: The ABR results from both the LS CE-Chirp^® and click stimuli were consistent and reliable over the two clinical sessions suggesting that both stimuli can be used for neurological diagnoses with the same reliability.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.5
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• pp.1144-1150
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• 2015

Presence information provides various informations about users such as on-line status, current location, network connection method and connection address, and there are two kinds of presence information, SIP(Session Initiation Protocol) based presence information and XMPP(Extensible Massaging and Presence Protocol) based presence information. In this paper, a multiple server architecture that can handle these two kinds of presence information has been proposed. In this architecture, severs are added dynamically according to number of users to provide system scalability, and load of each server can be effectively controlled. In this system, a new XMPP stanza architecture and presence information data format are designed for load control. Furthermore message exchanging procedures between servers and users for dynamic server control has been also suggested. The performance of the proposed system has been analysed by simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.8A
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• pp.820-827
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• 2010

In these days, video applications for special purposes such as video conference systems among multiple users and video surveillance systems require multiple video connections and QoS guarantee. The video systems employ IEEE 802.11 Wireless LAN devices to support broadband wireless interfaces and easy internet accesses for cheaper prices. However, according to the current IEEE 802.11e HCCA standard, if more than three video sessions are established in WSTA services, some of them must share the TXOP because the available number of TSIDs for video transmission is two. In order to resolve the problem, we devised a method which can establish up to 15 video sessions by slightly modifying the frame structure while maintaining the compatibility with current standard. Our method is implemented on the NCTUns 4.0 network simulator, and evaluated not only numerically in terms of throughput, delay, and PSNR, but also experimentally in the sense of real video clips that are used as input to our simulation. The results showed that our method sufficiently guarantees the transmission bandwidth requested by each video session.

• Journal of the Korea Safety Management & Science
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• v.10 no.2
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• pp.155-162
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• 2008

The ubiquitous, which is developed for human's convenience, uses the concept of situation awareness that communicates with computer and performs a certain work without user's recognition. In order to collect the information of situation, many devices are required. Also, in the condition of ubiquitous middleware, priority is given to effective controls of various devices. There are many devices for collecting the information of situation awareness such as sensor, RFID, etc. Among them, in the use of RFID, the researcher performed the experiment, in which multiple readers were used depending on the necessity of awareness information, and found the problem of intervention between readers occurring when multiple readers are used. The paper handles the problem of intervention causing from using multiple readers and suggests middleware design module using session manager to solve the problem.

• Journal of the Korea Society of Computer and Information
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• v.18 no.4
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• pp.79-85
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• 2013

In SIP(Session Initiation Protocol) environment, the presence server should process SIP SUBSCRIBE request messages including multiple presence resources addresses from users, and also precess massive notification messages from the subscribed presence resources. The load of the presence server increases as number of users increase, and it limits system extendability. Therefore a new multiple presence servers architecture has been suggested in this research. In this architecture presence servers can be added dynamically and each server's load can be controlled effectively as number of users increase. Each presence server can monitor current load status of entire presence system by using presence event notification package which newly has been suggested in this paper. When a particular presence server's load increases over predefined limit, the presence service processing is distributed by selecting a server which has the smallest load, or by generating a new server dynamically. In this system the overall load of the entire system can be controlled optimally and extendability of the system can be increased. For this purpose a new presence event notification package and presence information data format have been suggested. The performance of the proposed system has been evaluated by experiments. They shows 44.3% increase in SUBSCRIBE message processing time, and 43.1% increase in Notification message processing time.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.778-780
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• 2002

The TLS protocol suite, which provides transport-layer security far the Internet, has been standardized in the IETF. A TLS session is an association between a client and a server, created by the TLS handshake Protocol. Sessions define a set of cryptographic securi쇼 parameters, which can be shared among multiple connections. The TLS protocol, however, does not address the specific method fur how to manage the existing TLS sessions on the host. This paper proposes an efficient management scheme TLS, based on the principles of trust management.

• Proceedings of the Korea Multimedia Society Conference
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• 2003.11b
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• pp.965-968
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• 2003

본 연구에서는 웹 기반 멀티미디어 공동 작업 환경에서의 다중 세션을 잘 유지하기 위하여 웹 노트 오류 제어를 위한 관리기에 대해서 기술한다. 웹 기반 멀티미디어 공동 작업 환경은 멀티미디어 협력 작업에 웹의 동기화 기술을 확장한 웹 노트, 즉 복제형 구조에 기반을 둔 응용 공유의 동작 원리를 이용하여 동기화를 수행할 수 있는 환경을 의미한다. 각 세션의 생성에 따라 서비스 제공자는 생성된 서비스 제공자 인스턴스를 생성하게 되고 이 인스턴스는 부모인 서비스 제공자의 자원을 이용하여 다수 세션을 지원한다. 이러한 환경에서의 웹 노트 오류 제어 시스템을 기술한다.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.843-846
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• 2003

In this paper, we have analyzed algorithm of physical layer, data link layer and MAC layer of Out-Of-Band (OOB) specified in the OpenCabl $e^{TM}$SCTE-55-2 2002$^{[3]}$ and designed architecture of the OOB processor. The OOB processor performs fundamental multiple access control for the OOB channel and extracts session key information from a EMM packet for descrambling MPEG-2 streams. In this paper, we have implemented a prototype board for the DVS167 OOB processor and verified it.t.