• Journal of Convergence for Information Technology
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• v.7 no.3
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• pp.91-96
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• 2017

IoT which is an abbreviation of Internet of Things refers to the communication network service among various objects such as people-people, objects-objects interconnection. The characteristic of IoT that enables direct connection among each device makes security to be considered as more emphasized factor. Though a security module such as an authentication protocol for resolving various security problems that may occur in the IoT environment has been developed, some weak points in security are still being revealed. Therefore, this paper proposes a method for including a protocol including gateway authentication procedure and mutual authentication between the devices and gateways. Protocols with additional authentication procedures can appropriately respond to attackers' spoofing attacks. In addition, important information in the message used for authentication process is protected by encryption or hash function so that it can respond to wiretapping attacks.

• The Journal of the Korea Contents Association
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• v.12 no.1
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• pp.9-16
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• 2012

Though Android-based smart phones are being released in Korea, Korean TTS engine is not built on them and Google has not announced service or software developer's kit related to Korean TTS officially. Thus, application developers who want to include Korean TTS capability in their application have difficulties. In this paper, we design and implement Android OS-based Korean TTS system and service. For speed, text preprocessing and synthesis libraries are implemented using Android NDK. By using Java's thread mechanism and the AudioTrack class, the response time of TTS is minimized. For the test of implemented service, an application that reads incoming SMS is developed. The test shows that synthesized speech are generated in real-time for random sentences. By using the implemented Korean TTS service, Android application developers can transmit information easily through voice. Korean TTS service proposed and implemented in this paper overcomes shortcomings of the existing restrictive synthesis methods and provides the benefit for application developers and users.

• Journal of Korea Multimedia Society
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• v.10 no.3
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• pp.348-357
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• 2007

One of the major issues in recent researches on wireless sensor networks is to reduce energy consumption of sensor nodes operating with limited battery power, in order to lengthen their lifespan. Among the researches, we are interested in the schemes in which a sensor node periodically turns on and off its radio and requires information on the time when its neighbors will wake up (or turn on). Clock synchronization is essential for wakeup scheduling in such schemes. This paper proposes three methods based on the asynchronous averaging algorithm for clock synchronization in sensor nodes which periodically wake up: (1) a fast clock synchronization method during an initial network construction period, (2) a periodic clock synchronization method for saving energy consumption, and (3) a decision method for switching the operation mode of sensor nodes between the two clock synchronization methods. Through simulation, we analyze maximum clock difference and the number of messages required for clock synchronization.

• Journal of Navigation and Port Research
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• v.33 no.6
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• pp.395-400
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• 2009

In order to prepare for the DGNSS recapitalization and implementation of the functions for software based reference station and integrity monitor (RSIM) system, this paper proposes a design of integrity monitor functions of maritime differential GPS RSIM. The most critical functions of the integrity monitor (IM) are to generate and send flags to the reference station (RS) along with system feedback. Firstly, it presents the architecture of software based RSIM, and analyzes the performance standard of integrity monitor for maritime DGPS reference station This paper then designs the functions of integrity monitor for DGPS reference station based on the performance standard. Finally, this paper presents the results of performance analysis for the functionality of integrity monitor using the GNSS simulator. it discusses the study method and its application for the system implementation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.728-731
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• 2008

Recently demands in construction of the stand-alone networks and interconnection between convergence devices have led an increase in research on IETF MANET working group, Bluetooth, and HomeRF working group and much attention has been paid to the application of MANET as a Ubiquitous network which is growing fast. With performance both as hosts and routers, easy network configuration, and fast response, mobile nodes participating in MANET are suitable for Embedded computing, but have vulnerable points, such as lack of network scalability and dynamic network topology due to mobility, passive attacks, active attacks, which make continuous security service impossible. For perfect MANET setting, routing is required which can guarantee security and efficiency through secure routing. In routing in this study, hashed AODV is used to protect from counterfeiting messages by malicious nodes in the course of path 'finding and setting, and disguising misrouted messages as different mobile nodes and inputting them into the network.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.585-588
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• 2007

With several enhanced access technologies, users have many changes to select their preference access network. There are great differences between access technologies, users' need to handover from one access network to another is getting bigger. As users' need grows there are several works to archive fast handover between heterogeneous and homogeneous access networks. However traditional handover mechanisms work only on L2 or L3 have several limits that prevent fast and heterogeneous handover. To overcome those limits, IEEE 802.21 WG and IRTF MOBOPTS RG are working for developing handover mechanisms that uses L2 information on theupper layers like L3. This paper introduces two new L2 information and properties can be used to archive fast handover of mobile nodes.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.6
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• pp.453-460
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• 2014

We analyze fault detection algorithm of ephemeris included in navigation message, which is one of the GNSS risk factors. This algorithm uses carrier-phase measurement and baseline vector of two reference stations and is alternative method for uncertainty condition of previous ephemeris. Even though same ephemeris fault is occurred, the geometry condition, between baseline vector of reference stations and satellites, effects on performance of algorithm. Also, we introduce the suitable geometry of reference stations, threshold and performance index (MDE : Minimum Detectable Error) in jeju international airport.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.5
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• pp.921-928
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• 2017

Unlike wired networks, broadcasting in wireless networks can transmit data to several nodes at a time in a single transmission. The omnidirectional broadcasting of node in wireless networks simultaneously reaches all neighboring nodes. In this paper, we propose a greedy algorithm to solve the minimum power broadcasting problem that minimizes the total transmission power when broadcasting in wireless networks. The proposed algorithm uses a neighborhood list which is a set of nodes that can transmit messages within the maximum transmission range of each node, and among the transmitting nodes that have received the data, the node having the largest number of the neighboring nodes firstly transmits the data to neighboring node. The performance of the proposed algorithm was evaluated by computer simulation, and was compared with existing algorithms in terms of total transmission power and broadcasting frequency for broadcasting to all nodes. Experiment results show that the proposed algorithm outperforms the conventional algorithms.

• The KIPS Transactions:PartD
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• v.12D no.1 s.97
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• pp.21-30
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• 2005

In mobile computing environments, a mobile host caches the data to use the narrow bandwidth efficiently and improve the response time. A server periodically broadcasts the update data for maintaining the cache consistency of a mobile host. However, a method for maintaining cache consistency using periodic invalidation report has a problem that defers the commit decision of a mobile transaction to guarantee its serializable execution. In this paper, we propose CCM-AD method that guarantees the serializable execution of a mobile transaction even in the case that it is executed using cached data. As CCM-AD method guarantees the serializable execution of mobile transactions by using the intersection between the data broadcast to mobile host and the data updated at server. Then the CCM-AD method can reduce the delay of commitment decision of a mobile transaction. Also our method can reduce the size of invalidation report.

• The KIPS Transactions:PartC
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• v.10C no.1
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• pp.17-26
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• 2003

Mobile agent system comes into the spotlight since it contributes largely to mobile computing on distributed network environment. However, this system has a number of significant security Problems. In this Paper, we analyze suity attacks to mobile agent system Presented by NIST[3]. In order to protect this system from them, we suggest a security protocol for mobile agent system by employing R based key distribution and digital multi-signature scheme. To solve these problems described in NIST, securities for mobile agent and agent platform shouid be accomplished. Comparing with other protocols, our protocol performs both of these securities, while other protocols mentioned only one of them. Proposed Protocol satisfies simplicity of key management, providing security service such as confidentiality, integrity, authentication and preventing reputation, liveness guarantee, protection of excution-result data and preventing replay attack. Furthermore, it is designed to detect message modification immediately by verifying each step of agent execution at a corresponding server.