• Journal of the Korea Society of Computer and Information
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• v.18 no.8
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• pp.95-104
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• 2013

DDoS attacks have became as a social threat since 2009 7.7 DDoS turmoil. Even though defence techniques have been developing to provide against those threats, they become much more sophisticate. In recent years, the attack form of DDoS is changing from high amount of traffic attack of network layers to highly sophisticate small amount of application layers. To make matters worse, attack agent for the attack has became very intelligent so that it is difficult to be blocked since it can't be distinguished from normal PCs. In the user authentication system(such as CAPTCHA) User intervention is required to distinguish normal PCs and intelligent attack agents and in particular, in a NAT environment, IP-based blocking method can be cut off the normal users traffic at the same time. This research examined defense techniques which are able to distinguish between agent and normal PC and effectively block ways the HTTP DDoS offense applying one-time session key based authentication method using Cookie which is used in HTTP protocol to protect web sever from sophisticate application layer of DDoS.

• Journal of KIBIM
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• v.11 no.3
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• pp.45-54
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• 2021

The augmented reality (AR) has recently became an attractive technology in construction industry, which can play a critical role in realizing smart construction concepts. The AR has a great potential to help construction workers access digitalized information about design and construction more flexibly and efficiently. Though several AR applications have been introduced for on-site made to enhance on-site and off-site tasks, few are utilized in actual construction fields. This paper proposes a new AR framework that provides on-site managers with an opportunity to easily access the information about construction resources such as workers and equipment. The framework records videos with the camera installed on a wearable AR device and streams the video in a server equipped with high-performance processors, which runs an object detection algorithm on the streamed video in real time. The detection results are sent back to the AR device so that menu buttons are visualized on the detected objects in the user's view. A user is allowed to access the information about a worker or equipment appeared in one's view, by touching the menu button visualized on the resource. This paper details implementing parts of the framework, which requires the data transmission between the AR device and the server. It also discusses thoroughly about accompanied issues and the feasibility of the proposed framework.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.6
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• pp.1263-1268
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• 2018

In this paper, a video analysis is proposed to implement video surveillance system with deep learning object detection and probabilistic data association filter for tracking multiple objects, and suggests its implementation using GPU. The proposed video analysis technique involves object detection and object tracking sequentially. The deep learning network architecture uses ResNet for object detection and applies probabilistic data association filter for multiple objects tracking. The proposed video analysis technique can be used to detect intruders illegally trespassing any restricted area or to count the number of people entering a specified area. As a results of simulations and experiments, 48 channels of videos can be analyzed at a speed of about 27 fps and real-time video analysis is possible through RTSP protocol.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.307-309
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• 2016

This paper present about the system for sensing and controlling a wireless power transfer system using bluetooth protocol in robot, healthcare, smart-grid, and autonomous car. Recently a variety of applications using the Internet of Things (Internet of Things) and machine to machine (Machine to Machine) have been raised in many industries. To do this, it requires the fusion technology which is constituted with control, computing and networking. Embedded system is centered existing control system and Cyber Physical System(CPS) is the systems which was converged of a computing technologies using a wired or wireless network. CPS was adopted in the future government-led technology in the United States and Europe and is being pursued in cooperation with institutes, industries, and academia. In this paper, we implement and describe a technique for controlling the system for transmitting power wirelessly by sensing method using the matching of CPS technology concepts.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.2
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• pp.711-732
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• 2019

Many unmanned aerial vehicle (UAV) applications have been employed for performing data collection in facilitating tasks such as surveillance and monitoring objectives in remote and dangerous environments. In light of the fact that most of the existing UAV relaying applications operate in conventional half-duplex (HD) mode, a full-duplex (FD) based UAV relay aided wireless network is investigated, in which the UAV relay helps forwarding information from the source (S) node to the destination (D). Since the activated UAV relays are always floating and flying in the air, its channel state information (CSI) as well as channel capacity is a time-variant parameter. Considering decode-and-forward (DF) relaying protocol in UAV relays, the cooperative relaying channel capacity is constrained by the relatively weaker one (i.e. in terms of signal-to-noise ratio (SNR) or signal-to-interference-plus-noise ratio (SINR)) between S-to-relay and relay-to-D links. The channel capacity can be optimized by adaptively optimizing the transmit power of S and/or UAV relay. Furthermore, a hybrid HD/FD mode is enabled in the proposed UAV relays for adaptively optimizing the channel utilization subject to the instantaneous CSI and/or remaining self-interference (SI) levels. Numerical results show that the channel capacity of the proposed UAV relay aided wireless networks can be maximized by adaptively responding to the influence of various real-time factors.

• Journal of Digital Convergence
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• v.17 no.1
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• pp.195-201
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• 2019

This paper proposes a blockchain system to share Wireless Local Area Network (WLAN) that recently suffers from mutual interference among increasing devices using unlicensed bands. Blockchain technology can induce cooperation from users by incentivizing them with cryptocurrency like shown in Bitcoin example. In this paper, we describe Blockchain based access mechanism in WLAN instead of conventional authentication based access. Here, users can access any WLAN access point by paying through smart contract while they also receive payment from others. In order to support real-time transaction, we apply proof-of-authority that is realized by Byzantine fault tolerant protocol instead of well-known proof-of-work that requires huge computing power and delay.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.10
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• pp.1353-1358
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• 2021

IoT (Internet of Things) emerges from various technologies such as communications, micro processors and embedded system and so on. The IoT has also been used to UAV (Unmanned Aerial Vehicle) system. In manned aircraft, a pilot and co-pilot should control FCS (Flight Control System) with FBW(Fly By Wire) system for flight operation. In contrast, the flight operation in UAV system is remotely and fully managed by GCS (Ground Control System) almost in real time. To make it possible the communication channel should be necessary between the UAV and the GCS. There are many protocols between two systems. Amongst them, MAVLink (Macro Air Vehicle Link) protocol is representatively used due to its open architecture. MAVLink does not define any securities itself, which results in high vulnerability from external attacks. This paper proposes the method to enhance data security in GCS network by applying cryptographic methods to the MAVLink messages in order to support safe UAV operations.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.3
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• pp.103-118
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• 2002

To provide the privacy of transmitted message over network the use of cryptographic system is increasing gradually. Because the security and reliability of the cryptographic system is totally rely on the key, the key management is the most important part of the cryptographic system. Although there are a lot of security products providing encryption, the security of the key exchange protocols used in the product are not mostly proved yet. Therefore, we have to study properties and operation of key agreement protocols based on elliptic curve in ANSI X9.63. furthermore, we analyze the security of their protocols under passive and active attacker models and propose the most suitable application field taking the feature of the protocols into account.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.3
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• pp.53-65
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• 2010

Conditional Access System (CAS) is a core security mechanism of IPTV SCP (Service and Content Protection) which enables only authenticated user to be able to watch the broadcasting contents. In the past, it was general that CAS was built in Set-Top Box (STB) as hardware or as a detachable cable card. However, numerous researches in Downloadable CAS (DCAS), where users can download CAS code in their STB through their network, have been recently conducted widely due to the lack of security and scalability problem. In this paper, the security requirements of OpenCable based DCAS which is typical example of downloadable IPTV SCP will be derived, the novel authentication and key management scheme will be proposed by using the Authentication Proxy (AP) which is the core DCAS. Also, the benefits of the proposed system will be evaluated by comparison and analysis with preceding research.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.4
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• pp.1293-1316
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• 2021

Using directional antennas in wireless Ad hoc networks has many superiorities, including reducing interference, extending transmission range, and increasing space division multiplexing. However, directional transmission introduces two problems: deafness and directional hidden terminals problems. We observe that these problems result in saturation throughput disparity among the competing flows in directional CSMA/CA based Ad hoc networks and bring challenges for modeling the saturation throughput of the flows. In this article, we concentrate on how to model and analyze the saturation throughput disparity of different flows in directional CSMA/CA based Ad hoc networks. We first divide the collisions occurring in the transmission process into directional instantaneous collisions and directional persistent collisions. Then we propose a four-dimensional Markov chain to analyze the transmission state for a specific node. Our model has three different kinds of processes, namely back-off process, transmission process and freezing process. Each process contains a certain amount of continuous time slots which is defined as the basic time unit of the directional CSMA/CA protocols and the time length of each slot is fixed. We characterize the collision probabilities of the node by the one-step transition probability matrix in our Markov chain model. Accordingly, we can finally deduce the saturation throughput for each directional data stream and evaluate saturation throughput disparity for a given network topology. Finally, we verify the accuracy of our model by comparing the deviation of analytical results and simulation results.