• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.8
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• pp.1155-1160
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• 2013

The rapid growth of smart phones has made location-based services (LBSs) widely available. However, the use of LBS can raise privacy issues, as LBS can allow adversaries to violate the location privacy of users. There has been a considerable amount of research on preserving user location privacy. Most of these studies try to preserve location privacy by achieving what is known as location K-anonymity. In this paper, we propose a hierarchical clustering-based spatial cloaking algorithm for LBSs. The proposed algorithm constructs a tree using a modified version of agglomerative hierarchical clustering. The experimental results show, in terms of the ASR size, that the proposed algorithm is better than Hilbert Cloak and comparable to RC-AR (R-tree Cloak implementation of Reciprocal with an Asymmetric R-tree split). In terms of the ASR generation time, the proposed algorithm is much better in its performance than RC-AR and similar in performance to Hilbert Cloak.

• Journal of the Korea Society of Computer and Information
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• v.18 no.3
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• pp.47-57
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• 2013

Location privacy has been a serious concern for mobile users who use location-based services to acquire geographical location continuously. Spatial cloaking technique is a well-known privacy preserving method, which blurs an exact user location into a cloaked area to meet privacy requirements. However, cloaking for continuous moving object suffers from cloaked area size problem as it is unlikely for all objects travel in the same direction. In this paper, we propose a grid-based privacy preservation method with an improved Earth Mover's Distance(EMD) metric weight update scheme for semantic cloaking. We also define a representative cloaking area which protects continuous location privacy for moving users. Experimental implementation and evaluation exhibit that our proposed method renders good efficiency and scalability in cloaking processing time and area size control. We also show that our proposed method outperforms the existing method by successfully protects location privacy of continuous moving objects against various adversaries.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2010.06a
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• pp.53-60
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• 2010

위치 기반 서비스(Location-Based Services: LBS)에서 질의 요청자가 자신의 위치 정보와 원하는 질의를 전송하면, 위치 기반 서버는 이를 기반으로 질의를 처리하고 결과를 전송한다. 이 때 질의 요청자는 자신의 정확한 위치 좌표를 서버에 전송하기 때문에 개인 정보가 악용될 수 있는 위험에 노출된다. 이러한 문제를 해결하기 위하여 제안된 연구는 크게 Location Clocking 기법과 Private Information Retrieval(PIR) 기법으로 분류된다. Location Cloaking 기법은 사용자의 위치 좌표를 k-1개의 다른 사용자와 함께 묶어 하나의 Cloaking 영역을 생성하고 이를 바탕으로 질의를 처리한다. 그러나 영역에 대한 질의 후보 집합을 결과로 전송하므로 사용자에게 노출되는 POI 수가 증가하는 문제점을 지닌다. PIR은 암호화 기법으로 위치 기반 서버나 공격자에게 사용자의 위치와 질의 타입을 드러내지 않고 질의를 수행한다. 그러나 암호화 된 질의 결과로 사용자에게 데이터 전체를 전송하기 때문에 막대한 통신비용을 초래한다. 따라서 본 논문에서는 Location Cloakng과 PIR 기법의 장점을 결합하여 사용자의 개인 정보와 위치 기반 서버의 POI 정보 보호를 고려한 Approximate k-최근접점 질의 처리 알고리즘을 제안한다. 질의 전송시, 질의 요청자는 Cloaking 영역을 생성하여 위치 좌표를 감추고, 질의 결과 전송 시 Cloaking 영역에 제한된 PIR 프로토콜을 적용한다. 또한 k-최근접점 질의 수행시, 반환되는 POI의 수를 최소화하고, 정확도 높은 질의 결과를 만족하기 위해 Overlapping parameter를 적용한 색인 기법을 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.41-44
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• 2011

논문은 위치기반 서비스에서 사용자의 위치 정보를 보호하기 위해 필요한 요구사항들을 정리하고, 기존에 연구되었던 기법들을 비교 분석하여 앞에서의 요구사항을 얼마나 충족하는지에 대하여 살펴본다. 또한 기존의 기법들이 충족하지 못하는 부문을 해결하기 위하여 시간대별로 통계화된 밀도 정보를 기반으로 Cloaking 영역을 생성하는 기법을 제안하여 사용자들이 위치기반 서비스를 사용함에 있어서 기존의 기법보다 더 효율적으로 사용자의 위치정보를 보호할 수 있음을 보인다.

• Korean Journal of Mathematics
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• v.23 no.1
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• pp.171-180
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• 2015

It is discovered in [7] that a dielectric material is coated by a plasmonic material of negative permittivity with dissipation, then cloaking by anomalous localized resonance may occur as the dissipation tends to zero. In this paper, we investigate numerically the pointwise behavior of the potential in the shell when cloaking by anomalous localized resonance (CALR) occurs. By changing locations a dipole source, we can observe some localizing properties of the potential in the shell.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.11a
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• pp.697-698
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• 2009

모바일 기기 및 무선 통신 기술의 발달로 인하여 위치 기반 서비스의 이용이 확산되었다. 그러나 이와 같이 사용자의 정확한 위치정보를 가지고 LBS 서버에 서비스를 요청하는 것은 심각한 개인 정보 누출의 위협이 될 수 있다. 따라서 안전하고 편리한 위치기반 서비스 사용을 위한 개인 정보 보호 방법이 요구된다. 이를 위해 본 논문에서는 연속적인 위치기반 서비스를 지원하는 분산 그리드 기반 Cloaking 영역 설정 기법을 설계한다. 설계하는 기법은 분산 환경에서 연속적인 서비스를 지원하기 위해 Cloaking 영역 설정 시 필요한 정보를 분산 유지하고, 이동 확률 매트릭스 생성 및 확률 계산을 분산적으로 수행한다. 마지막으로는 모바일 사용자 사이에 발생하는 통신비용을 감소시키기 위해, 대표 노드는 해당 클러스터에서 떠난 사용자에 대한 정보를 유지하고 클러스터 내 부분 확률값의 합산시 병합노드를 사용한다.

• Spatial Information Research
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• v.20 no.5
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• pp.57-66
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• 2012

Recent development in wireless communication technology like GPS as well as mobile equipments like PDA and cellular phone makes location-based services (LBSs) popular. However, because users request a query to LBS servers by using their exact locations while moving on the road network, users' privacy may not be protected in the LBSs. Therefore, a mechanism for users' privacy protection is required for the safe and comfortable use of LBSs by mobile users. For this, we, in this paper, propose a road network distance based cloaking scheme supporting user privacy protection in location-based services. The proposed scheme creates a cloaking area by considering road network distance, in order to support the efficient and safe LBSs on the road network. Finally, we show from our performance analysis that our cloaking scheme outperforms the existing cloaking scheme in terms of cloaking area and service time.

• Journal of Internet Computing and Services
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• v.15 no.6
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• pp.9-14
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• 2014

In this paper, we propose AMV scheme which supports k-anonymization by using vectors for mobile clients. AMV can produces the minimal cloaking area using motion vector information of users (clients). The main reason for minimizing cloaking area is a server has to send the object information to all users who request the spatial queries. The experimental results show that the proposed AMV has superior performance over existing methods.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.10
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• pp.3438-3457
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• 2022

As location-based services (LBS) are widely used in vehicular ad-hoc networks (VANETs), location privacy has become an utmost concern. Spatial cloaking is a popular location privacy protection approach, which uses a cloaking area containing k-1 collaborative vehicles (CVs) to replace the real location of the requested vehicle (RV). However, all CVs are assumed as honest in k-anonymity, and thus giving opportunities for dishonest CVs to submit false location information during the cloaking area construction. Attackers could exploit dishonest CVs' false location information to speculate the real location of RV. To suppress this threat, an edge-assisted Trusted Collaborative Anonymity construction scheme called TCA is proposed with trust mechanism. From the design idea of trusted observations within variable radius r, the trust value is not only utilized to select honest CVs to construct a cloaking area by restricting r's search range but also used to verify false location information from dishonest CVs. In order to obtain the variable radius r of searching CVs, a multiple linear regression model is established based on the privacy level and service quality of RV. By using the above approaches, the trust relationship among vehicles can be predicted, and the most suitable CVs can be selected according to RV's preference, so as to construct the trusted cloaking area. Moreover, to deal with the massive trust value calculation brought by large quantities of LBS requests, edge computing is employed during the trust evaluation. The performance analysis indicates that the malicious response of TCA is only 22% of the collaborative anonymity construction scheme without trust mechanism, and the location privacy leakage is about 32% of the traditional Enhanced Location Privacy Preserving (ELPP) scheme.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.77.2-77.2
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• 2015

Recently, metamaterials attracted much attention because of the potential applications for superlens, cloaking and high precision sensors. We developed several dielectric metamaterials for enhancing antireflection or light trapping capability in solar energy harvesting devices. Colloidal lithography and electrochemical anodization process were employed to fabricate self-assembed nano- and microscale dielectric metamaterials in a simple and cost-effective manner. We improved broadband light absorption in c-Si, a-Si, and organic semiconductor layer by employing polystyrene (PS) islands integrated Si conical-frustum arrays, resonant PS nanosphere arrays, and diffusive alumina nanowire arrays, respectively. We also demonstrated thin metal coated alumina nanowire array which is utilized as an efficient light-to-heat conversion layer of solar steam generating devices. The scalable design and adaptable fabrication route to our light management nanostructures will be promising in applications of solar energy harvesting system. On the other hands, broadband invisible cloaks, which continuously work while elastically deforming, are developed using smart metamaterials made of photonic and elastic crystals. A self-adjustable, nearly lossless, and broadband (10-12GHz) smart meatamaterials have great potentials for applications in antenna system and military stealth technology.