• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5A
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• pp.527-536
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• 2004

A novel hybrid multiple access system, TD-BCDMA, where Binary CDMA that maintains a constant amplitude by clipping the summation of input signals multiplied by the orthogonal codes is transmitted over a TDMA frame structure, was Nosed. In every time slot of TDMA, binary CDMA modulated multiple channel signals are transmitted with the same waveform of TDMA. TD-BCDMA has all the advantages of TDMA. Flexible adjustment of the data transmission rate In demand is possible by adjusting the number of codes and time slots assigned to each user. This property was used to show an example of Ad Hoc network applications. To obtain a proper synchronization scheme for TD-BCDMA, the Receiver Operating Characteristics performance and the false alarm probability and false dismissal probability under various channel environment of two different schemes, a preamble scheme as in TDMA and a synchronization channel scheme as in CDMA were compared. It was proved that the preamble scheme is more practical and suitable than the synchronization channel scheme for the hybrid multiple access system.

• The KIPS Transactions:PartD
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• v.13D no.7 s.110
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• pp.977-984
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• 2006

This paper is intended to trace and management of drug based on RFID Technology at a circulation market, from manufacturer to end user, of drug. To avoid counterfeit and generic drug and establish of order in the circulation of drug, at the moment of manufacturing, tags for each bottle and each box are tagged. and then from factory to hospital, through whole logistics, e-pedigree for the drug is made and monitored. Using inventory information, it is easy to manage and control stock of drug. In addition to, RFID System enables storing and delivery to be simple, process time to be shortened. As this research is to study of applying RFID to drug, in this paper, standard RFID code for drug is suggested and tried to apply domestic middle win. Finally, the result of tag pattern design and how to tag for the drug based on 90Mhz is proposed

• The KIPS Transactions:PartB
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• v.19B no.2
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• pp.83-92
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• 2012

Multimedia contents can be copied and manipulated without quality degradation. Therefore, they are vulnerable to digital forgery and illegal distribution. In these days, with increasing the importance of multimedia security, various multimedia security techniques are studied. In this paper, we propose a content authentication algorithm based on reversible watermarking which supports JPEG compression commonly used for multimedia contents. After splitting image blocks, a specific authentication code for each block is extracted and embedded into the quantized coefficients on JPEG compression which are preserved against lossy processing. At a decoding process, the watermarked JPEG image is authenticated by extracting the embedded code and restored to have the original image quality. To evaluate the performance of the proposed algorithm, we analyzed image quality and compression ratio on various test images. The average PSNR value and compression ratio of the watermarked JPEG image were 33.13dB and 90.65%, respectively, whose difference with the standard JPEG compression were 2.44dB and 1.63%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.6
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• pp.360-369
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• 2014

Underwater Acoustic Sensor Networks(UASN) enables varied study from collected data of underwater environments such as pollution monitoring, disaster prevention. The collected data is transmitted from underwater to terrestrial communication entity by acoustic communication. Because of the constraints of underwater environments include low data rate and propagation delay, it is difficult to apply cryptographic techniques of terrestrial wireless communication to UASN. For this reason, if the cryptographic techniques are excluded, then collected data will be exposed to security threats, such as extortion and forgery, during transmission of data. So, the cryptographic techniques, such as the authentication and key establishment protocol which can confirm reliability of communication entities and help them share secret key for encryption of data, must need for protecting transmitted data against security threats. Thus, in this paper, we propose the light weight authentication and key establishment protocol.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.5
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• pp.999-1008
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• 2017

In this paper, we propose a pipeline network coding (PNC) scheme for efficient data transmission in wireless networks, a data authentication scheme for verifying the integrity of data, and a node authentication scheme for a virtual source. PNC is a technique that improves the overall network performance by relaying data such that the relay node performing network coding transmits to the sender instead. However, network coding is vulnerable to a pollution attack, which is an attack by a malicious attacker to inject modified data into the network. To prevent this, hash-based message authentication code (HMAC) is used. For this purpose, in order to generate a tag used for data authentication, a key must be distributed to the nodes performing authentication. We applied a hash chain to minimize the overhead of key distribution. A null vector is used as the authentication scheme for the virtual source. Finally, we analyze the safety and complexity of the proposed scheme and show he performance through simulation.

• Journal of the Society of Disaster Information
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• v.13 no.2
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• pp.267-275
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• 2017

This research is about the development of e-forensic tool that extract & analyze different forms of digital evidence that individuals come across in a disaster scene. The tool utilizes digital forensic techniques which makes the tool efficient in any disaster analysis situation. In order for the forensic evidence to be selected as legal evidence, the evidence needs to be proven that it is in its original state with no forgery involved. This is where the e-forensic tool comes in, as its ability to collect digital evidence during investigation has proven; that the tool can keep the evidence in its original state and increase the integrity by generating hash TAG and adding the forensic evidence to a password encoded file.

• Journal of the Korea Society of Computer and Information
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• v.16 no.8
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• pp.109-118
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• 2011

Recently, electronic documents are deployed in many areas. However, trust concerns arise owing to the fact that detecting whether an electronic document is modified or not is not an easy process. To facilitate this process, many word processors provide digital signature capabilities on themselves. However, there were not much research on the security of digital signature function of various programs including Microsoft Word and Hancom Hangul. Therefore, in this paper, we analyze the security of Microsoft Word and Hancom Hangul, and propose improvements for their digital signature schemes.

• Korean Journal of Optics and Photonics
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• v.19 no.1
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• pp.60-67
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• 2008

An all-optical 4-bit Gray code to binary coded decimal (BCD) converter by means of commercially available numerical analysis tool (VPI) was demonstrated, for the first time to our knowledge. Circuit design approach was modified appropriately in order to fit the electrical method on an all-optical logic circuit based on a cross gain modulation (XGM) process so that signal degradation due to the non-ideal optical logic gates can be minimized. Without regenerations, Q-factor of around 4 was obtained for the most severely degraded output bit (least significant bit-LSB) with 2.5 Gbps clean input signals having 20 dB extinction ratio. While modifying the two-level simplification method and Karnaugh map method to design a Gray code to BCD converter, a general design concept was also founded (one-level simplification) in this research, not only for the Gray code to BCD converter but also for any general applications.

• Korean Journal of Optics and Photonics
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• v.18 no.1
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• pp.79-83
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• 2007

A reconfigurable photonic microwave (MW) channel selective filter was demonstrated incorporating a $1{\times}2$ switch based on two tunable polymeric resonators with different free spectral ranges. Each resonator, consisting of two cascaded rings with an electrode formed on one of them, plays a role as an on/off switch through the thermooptic effect. The optical signal carrying the MW signal is routed to either port of the switch and detected to show the filtered output at the frequency determined by the free spectral range of the corresponding resonator. When the channel centered at 10 GHz was chosen, the extinction ratio was ${\sim}30dB$, the bandwidth 1 GHz, and the electrical power consumption 4.1 mW. For the other channel located at 20 GHz, we have achieved the extinction ratio of ${\sim}30dB$, the bandwidth of 2 GHz, and the required power of 8.0 mW. Finally the crosstalk between the selected and blocked channels was higher than 24 dB.