• KIISE Transactions on Computing Practices
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• v.22 no.3
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• pp.151-156
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• 2016

Cloud computing systems require a huge number of storage servers due to the growing implications of power bills, carbon emissions, and logistics of data centers. These considerations have motivated researchers to improve the energy efficiency of storage servers. Most servers use a lot of power irrespective of the amount of computing that they are doing, and one important goal is to redesign servers to be power-proportional. However, Research on large-scale storage systems is hampered by their cost. It is therefore desirable to develop a scalable test-bed for evaluating the power consumption of large-scale storage systems. We are building on open-source projects to construct a test-bed which will contribute to the assessment of power consumption in tiered storage systems. Integrating the cloud application platform can easily extend the proposed testbed laying a foundation for the design and evaluation of low-power storage servers.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.9
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• pp.3293-3311
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• 2015

Cloud services are required to be composed as a single service to fulfill the workflow applications. Service composition in Cloud raises new challenges caused by the diversity of users with different QoS requirements and vague preferences, as well as the development of cloud computing having geographically distributed characteristics. So the selection of the best service composition is a complex problem and it faces trade-off among various QoS criteria. In this paper, we propose a Cloud service composition approach based on evolutionary algorithms, i.e., NSGA-II and MOPSO. We utilize the combination of multi-objective evolutionary approaches and Decision-Making method (AHP) to solve Cloud service composition optimization problem. The weights generated from AHP are applied to the Crowding Distance calculations of the above two evolutionary algorithms. Our algorithm beats single-objective algorithms on the optimization ability. And compared with general multi-objective algorithms, it is able to precisely capture the users' preferences. The results of the simulation also show that our approach can achieve a better scalability.

• Journal of Internet Computing and Services
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• v.13 no.5
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• pp.55-64
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• 2012

Nowadays, as Cloud computing becomes popular, a need for a DFS(distributed file system) is increased. But, in the current Cloud computing environments, there is no DFS framework that is sufficient to protect sensitive private information from attackers. Therefore, we designed and proposed a secure scheme for distributed file systems. The scheme provides confidentiality and availability for a distributed file system using a secret sharing method. In this paper, we measured the speed of encryption and decryption for our proposed method, and compared them with that of SEED algorithm which is the most popular algorithm in this field. This comparison showed the computational efficiency of our method. Moreover, the proposed secure read/write model is independent of Hadoop DFS structure so that our modified algorithm can be easily adapted for use in the HDFS. Finally, the proposed model is evaluated theoretically using performance measurement method for distributed secret sharing model.

• Journal of Internet Computing and Services
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• v.14 no.3
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• pp.23-33
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• 2013

Recently in the field of IT, cloud computing technology has been deployed rapidly in the current society because of its flexibility, efficiency and cost savings features. However, cloud computing system has a big problem of vulnerability in security. In order to solve the vulnerability of cloud computing systems security in this study, impact types of virtual machine about the vulnerability were determined and the priorities were determined according to the risk evaluation of virtual machine's vulnerability. For analyzing the vulnerability, risk measurement standards about the vulnerability were defined based on CVSS2.0, which is an open frame work; and the risk measurement was systematized by scoring for relevant vulnerabilities. Vulnerability risk standards are considered to suggest fundamental characteristics of vulnerability and to provide the degree of risks and consequently to be applicable to technical guides to minimize the vulnerability. Additionally, suggested risk standard of vulnerability is meaningful as the study content itself and could be used in technology policy project which is to be conducted in the future.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.1
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• pp.1-17
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• 2017

Mobile Cloud Computing has become a promising computing platform. It moves users' data to the centralized large data centers for users' mobile devices to conveniently access. Since the data storage service may not be fully trusted, many public verification algorithms are proposed to check the data integrity. However, these algorithms hardly consider the huge computational burden for the verifiers with resource-constrained mobile devices to execute the verification tasks. We propose an energy-efficient algorithm for assigning verification tasks (EEAVT) to optimize the energy consumption and assign the verification tasks by elastic and customizable ways. The algorithm prioritizes verification tasks according to the expected finish time of the verification, and assigns the number of checked blocks referring to devices' residual energy and available operation time. Theoretical analysis and experiment evaluation show that our algorithm not only shortens the verification finish time, but also decreases energy consumption, thus improving the efficiency and reliability of the verification.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.12
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• pp.6098-6122
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• 2018

Cache-based side-channel attacks have achieved more attention along with the development of cloud computing technologies. However, current host-based mitigation methods either provide bad compatibility with current cloud infrastructure, or turn out too application-specific. Besides, they are defending blindly without any knowledge of on-going attacks. In this work, we present CacheSCDefender, a framework that provides a (Virtual Machine Monitor) VMM-based comprehensive defense framework against all levels of cache attacks. In designing CacheSCDefender, we make three key contributions: (1) an attack-aware framework combining our novel dynamic remapping and traditional cache cleansing, which provides a comprehensive defense against all three cases of cache attacks that we identify in this paper; (2) a new defense method called dynamic remapping which is a developed version of random permutation and is able to deal with two cases of cache attacks; (3) formalization and quantification of security improvement and performance overhead of our defense, which can be applicable to other defense methods. We show that CacheSCDefender is practical for deployment in normal virtualized environment, while providing favorable security guarantee for virtual machines.

• Proceedings of the KAIS Fall Conference
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• 2012.05b
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• pp.524-526
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• 2012

본 연구에서는 클라우드 서비스 확산에 필요한 유틸리티 컴퓨팅의 과금체계에 대해 살펴보았다. 클라우드 컴퓨팅에서 요구하는 조건들을 만족하는 과금정책을 제시한 후, 다양한 과금정책들을 비교 평가할 수 있는 지표로 작업 서비스 품질 만족도와 클러스터 수익성을 제시한다.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.10
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• pp.429-436
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• 2017

There is a growing tendency to outsource sensitive or important data in cloud computing recently. However, it is very important to protect the privacy of outsourced data. So far, a variety of secure and efficient multi-keyword search schemes have been proposed in cloud computing environment composed of a single data owner and multiple data users. Zhang et. al recently proposed a search protocol based on multi-keyword in cloud computing composed of multiple data owners and data users but their protocol has two problems. One is that the cloud server can illegally infer the relevance between data files by going through the keyword index and user's trapdoor, and the other is that the response for the user's request is delayed because the cloud server has to execute complicated operations as many times as the size of the keyword index. In this paper, we propose an improved multi-keyword based search protocol which protects the privacy of outsourced data under the assumption that the cloud server is completely unreliable. And our experiments show that the proposed protocol is more secure in terms of relevance inference between the data files and has higher efficiency in terms of processing time than Zhang's one.

• The Journal of Information Systems
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• v.22 no.2
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• pp.85-104
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• 2013

최근 클라우드 컴퓨팅이 학계나 실무계에서 많은 주목을 받고 있으며, 공공기관에서도 클라우드 컴퓨팅을 도입하고 있는 추세에 있다. 클라우드 컴퓨팅은 장 단점을 모두 가지고 있지만 지속적으로 발전하고 있으며, 기업들은 클라우드 기반의 정보시스템을 도입하기 위한 다양한 솔루션들을 활용하고 있다. 따라서 기업에서 클라우드 컴퓨팅 도입을 위해 고려해야 할 요소들은 무엇이며, 어떻게 계획을 수립할 것인지는 시급한 과제라고 할 수 있다. 본 논문의 목적은 기업이 클라우드 컴퓨팅 채택 전략을 수립하기 위한 프레임 워크를 제시하는 것이다. 구체적으로, SWOT-AHP는 클라우드 컴퓨팅을 실행하는 과정에서 강점-약점-기회-위협 요인을 파악하고, 전략 계획을 보다 효율적으로 수립 하는데 사용된다. 경영전략 이론에서 널리 알려져 있는 SWOT과 다기준의사결정기법 중 실무에서 가장 활발하게 사용되고 있는 AHP는 복잡하지 않고 적용이 쉽기 때문에 본 연구에서 제안하는 방법을 이용한다면 실무에서도 큰 어려움 없이 SWOT-AHP 프레임워크를 클라우드 컴퓨팅 전략수립에 적용할 수 있을 것으로 기대한다.

• Journal of the Korea Society of Computer and Information
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• v.16 no.2
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• pp.217-224
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• 2011

Existing wire based physical security system solutions show limitations in time and space. In order to solve these deficiencies, a remote physical security system has been implemented using smart phone based on mobile cloud computing technique. The security functions of mobile cloud computing technique include mobile device user authentication, confidentiality of communication, integrity of information, availability of system, and target system access control, authority management and secure hand off etc. Proposed system has been constructed as remote building management system using smart phone, and also has been efficient to reduce energy cost (5~30%), result of system average access and response time 7.082 second. This systems are evaluated to have high efficiency compared to performance.