• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.11
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• pp.1034-1042
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• 2004

In this paper, as one of countermeasure techniques for a frequency selective fading, an adaptive analog slope equalizer(ASE) applicable to 64-QAM digital radio relay system is presented in terms of principle, implementation, and its performance. Also interference of cross-talk between I- and Q-channel caused by a fiequency selective lading has been analyzed by doing channel model in the baseband, which make it possible to derive the solution for implementing ASE in If-band. The effects of signal for the faded channel are investigated in the time and the frequency domains, respectively, with/without ASE. As system performance, it is shown that the signature is improved up to 6.2 dB at the edge of signal bandwidth for a given BER 10$\^$-3/.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4B
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• pp.435-441
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• 2009

The one-time password system solves the problem concerning password reuse caused by the repeated utilization of an identical password. The password reuse problem occurs due to the cyclic repetition at the time of password creation, and authentication failure can occur due to time deviation or non-synchronization of the number of authentication. In this study, the password is created asynchronously and exchanged with the user, who then signs using a digital signature in exchange for the password and a valid verification is requested along with the certificate to ensure non-repudiation. Besides this, a verification system for one-time password is proposed and designed to improve security by utilizing the validity verification that is divided into certificate verification and password verification. Comparative analysis shows that the mechanism proposed in this study is better than the existing methods in terms of replay attack, non-repudiation and synchronization failure.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.6
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• pp.2922-2945
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• 2018

Achieving efficient authentication is a crucial issue for stream data commonly seen in content delivery, peer-to-peer, and multicast/broadcast networks. Stream authentication mechanisms need to be operated efficiently at both sender-side and receiver-side at the same time because of the properties of stream data such as real-time and delay-sensitivity. Until now, many stream authentication mechanisms have been proposed, but they are not efficient enough to be used in stream applications where the efficiency for sender and receiver sides are required simultaneously since most of them could achieve one of either sender-side and receiver-side efficiency. In this paper, we propose an efficient stream authentication mechanism, so called TIM, by integrating Trapdoor Hash Function and Merkle Hash Tree. Our construction can support efficient streaming data processing at both sender-side and receiver-side at the same time differently from previously proposed other schemes. Through theoretical and experimental analysis, we show that TIM can provide enhanced performance at both sender and receiver sides compared with existing mechanisms. Furthermore, TIM provides an important feature for streaming authentication, the resilience against transmission loss, since each data block can be verified with authentication information contained in itself.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.34
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• pp.157-185
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• 2007

The purpose of this thesis is to contribute to the activation of e-contract service for one stop e-trade by analyzing the problems and its solutions in e-contract service at home and abroad. In order to achieve the purpose of this thesis, case studies are done on e-contract service providers such as CECTRUST service of NTT DATA in Japan and HanCM.com of Haansoft in Korea and user companies such as Taisei Corporation using CECTRUST service and Hyundai Card using HanCM.com. The problems in the e-contract service are the lack of e-contract service providers, rare publicity of e-contract service, limited use of e-contract service at only home, higher pricing for e-contract service, short time management of e-contract documents by service providers, no application of newly developed security technology to e-contract service, unsatisfaction of requirements of e-contract service provider as trusted third party, absence of lower pricing e-contract service by service provider, authorizing key error in electronic signature under recognized authentication system in case of fail in renewal of digital certificate and reproduction of digital certificate. The solutions of these problems are the upbringing of e-contract service providers, broad publicity of e-contract service, development of e-contract service on a global basis, establishment of lower pricing for e-contract service, long time management of e-contract documents by service providers, application of newly developed security technology such as bio technology to e-contract service, satisfaction of requirements of e-contract service provider as trusted third party by designation of recognized e-document repository, development of lower e-contract service by way of application service provider(ASP), introduction of time stamping of e-contract document and signature key value. The limitation of this thesis is that the problems and its solutions could not meet with the broad recognition as they are conferred by intuition because of few e-contract service provider.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.1
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• pp.25-30
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• 2017

The influence of the data deletion method which is one of anti-forensic techniques is substantial in terms of forensic analysis compared to its simplicity of the act. In academic world, recovery techniques on deleted files have been continuously studied in response to the data deletion method and representatively, the file system-based file recovery technique and file format based recovery technique exist. If there's metadata of deleted file in file system, the file can be easily recovered by using it, but if there's no metadata, the file is recovered by using the signature-based carving technique or the file format based recovery technique has to be applied. At this time, in the file format based recovery technique, the file structure analysis and possible recovery technique should be provided. This paper proposes the page recovery technique on deleted PDF file based on the structural characteristics of PDF file. This technique uses the tag value of page object which constitutes one page of PDF file. Object is extracted by utilizing each tag value as a kind of signature and by analyzing extracted object, the metadata of PDF file is recombined and then it's reconfigured page by page. Recovering by page means that even if deleted PDF file is damaged, even some pages consisting of PDF file can be recovered. Generally, if the file system based file is not recoverable, deleted file is recovered by applying the signature based carving technique. The technique which we proposed in this paper can recover PDF files that are damaged. In the digital forensic perspective, it can be utilized to recover more data than previously.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10c
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• pp.287-289
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• 2000

처리시간 지연에 민감한 패킷 플로우, 비디오, 오디오 스트림과 같은 어플리케이션을 보안성이 없는 인터넷상에서 멀티캐스팅할 때에 데이터의 기밀성, 메시지 또는 발신자 인증, 무결성 그리고 부인 방지 등의 보안 서비스를 제공하기 위해서는 여러 가지 암호 및 인증 기법이 필요하다. 본 논문에서는 이러한 멀티캐스트 스트림과 플로우에 대한 서명/인증 기법의 특성과 요구사항을 분석해 보고 기존에 제시된 each-sign 기법, one-time 서명 기법, star-chaining 기법, 그리고 Tree-chaining 기법에 대한 상호 비교 및 분석을 통해 이들의 서명/검증 계산시간과 통신 트래픽 오버헤드에 대한 단점을 효율적으로 개선하여 Enhanced Tree-chaining 기법을 제안한다. 서명 및 검증 시간은 약 50% 단축되며 통신 오버헤드는 log2n배 축소되는 향상을 기대할 수 있다. 또한 인증 소요 시간에 주요 요인이 되는 것은 서명/검증의 계산시간이 아니라 chaining 오버헤드의 크기임을 유추해 낸다.

• Journal of Information Processing Systems
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• v.3 no.2
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• pp.82-88
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• 2007

Web services are the new building block of today's Internet, and provides interoperability among heterogeneous distributed systems. Recently in web services environment, security has become one of the most critical issues. The hackers attack one of fragile point and can misuse legitimate user privilege because all of the connected devices provide services for the user control and monitoring in real time. Also, the users of web services must temporarily delegate some or all of their rights to agents in order to perform actions on their behalf. This fact risks the exposure of user privacy information. In this paper, we propose secure delegation model based on SAML that provides confidentiality and integrity about the user information in distributed systems. In order to support privacy protection, service confidentiality, and assertion integrity, encryption and a digital signature mechanism is deployed. We build web service management server based on XACML, in order to manage services and policies of web service providers.

• Journal of Information Technology Services
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• v.19 no.3
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• pp.101-115
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• 2020

Electronic voting is one of information technology service to handle a wide range of functions, including registration, certification, input and results of voting, using electronic technology, depending on the degree of automation. It helps voters exercise their voting rights not only for individual suffrage but also for major corporate decisions as shareholders by expressing their opinions regardless of geographical and time constraints. Such electronic voting helps open and expand voting participation, but on the contrary, it is possible to identify who voted and what kind of vote, such voting cannot guarantee confidentiality. Therefore, if blockchain technology is applied to electronic voting, it can increase the speed of processing and confidentiality by encrypting voting information. In this regard, the study aims to identify institutional issues on how electronic voting can be activated at a company's shareholders' meeting, and to find ways to overcome the limitations of existing electronic voting by utilizing the technical characteristics of blockchain. This study proposes a consortium-type blockchain-based electronic voting system to enhance the convenience and reliability of electronic voting for shareholders' meetings. In addition, this paper suggests how to enhance shareholders' profits through electronic voting at shareholders' meetings, as well as its policy measures and future improvements.

• International journal of advanced smart convergence
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• v.8 no.2
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• pp.204-210
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• 2019

Mobile Crowd Computing is one of the most efficient and effective way to collect the Electronic health records and they are very intelligent in processing them. Mobile Crowd Computing can handle, analyze and process the huge volumes of Electronic Health Records (EHR) from the high-performance Cloud Environment. Electronic Health Records are very sensitive, so they need to be secured, authenticated and processed efficiently. However, security, privacy and authentication of Electronic health records(EHR) and Patient health records(PHR) in the Mobile Crowd Computing Environment have become a critical issue that restricts many healthcare services from using Crowd Computing services .Our proposed Efficient Multi-layer Encryption Framework(MLEF) applies a set of multiple security Algorithms to provide access control over integrity, confidentiality, privacy and authentication with cost efficient to the Electronic health records(HER)and Patient health records(PHR). Our system provides the efficient way to create an environment that is capable of capturing, storing, searching, sharing, analyzing and authenticating electronic healthcare records efficiently to provide right intervention to the right patient at the right time in the Mobile Crowd Computing Environment.

• Journal of Korea Multimedia Society
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• v.11 no.3
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• pp.315-322
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• 2008

Searching a location of the copied video in video database, signatures should be robust to video reediting, channel noise, time variation of frame rate. Several kinds of signatures has been proposed. Ordinal signature, one of them, is difficult to describe the spatial characteristics of frame due to the site of fixed window, $N{\times}N$, which is compute the average gray value. In this paper, I studied an algorithm of sequence matching in video copy detection for the copyright protection, employing the R-tree index method for retrieval and suggesting a robust ordinal signatures for the original video clips and the same signatures of the pirated video. Robust ordinal has a 2-dimensional vector structures that has a strong to the noise and the variation of the frame rate. Also, it express as MBR form in search space of R-tree. Moreover, I focus on building a video copy detection method into which content publishers register their valuable digital content. The video copy detection algorithms compares the web content to the registered content and notifies the content owners of illegal copies. Experimental results show the proposed method is improve the video matching rate and it has a characteristics of signature suitable to the large video databases.