• The Journal of Korean Physical Therapy
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• 제27권1호
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• pp.30-37
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• 2015

Purpose: The purpose of this study was to develop a computer access assessment tool for persons with physical disabilities and to evaluate reliability and validity. Methods: We developed a computerized Computer access Assessment Program (CAP) through many kinds of literature review and tools analysis for evaluation of computer access, task analysis of fundamental input devices operation and expert review. The CAP data were obtained from 105 normal university students and 16 students with physical disabilities. The test items of CAP are composed of four timed mouse tasks, four timed keyboard tasks, and a timed scanning task. Thus, the software measures user performance in skills needed for computer interaction, such as keyboard and pointer use, navigating through menus, and scanning. To determine the validity of these measurements, we compared data on CAP reports to a Compass report. Compass software allows an evaluator for assessment of an individual's computer input skills. Results: Results of this study showed that the CAP had high internal consistency, reliability of test-retest, concurrent validity, and convergent validity. Conclusion: Therefore, the CAP is appropriate for evaluation and determination of computer access skill of persons with physical disabilities. It is possible to get clear quantitative data on performance when providing computer access services if you can use the CAP data. Using this quantitative evidence, insights can be gained into the specific nature of any difficulties experienced by persons with physical disabilities and find wise solutions.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2013년도 춘계학술발표대회
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• pp.157-158
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• 2013

Data privacy and access control policies in computer clouds are a prime concerns while talking about the sensitive data. Authorized access is ensured with the help of secret keys given to a range of valid users. Granting the role access is a trivial matter but revoking user access is tricky and compute intensive. To revoke a user and making his data access ineffective the data owner has to compute new set of keys for the rest of effective users. This situation is inappropriate where user revocation is a frequent phenomenon. Time based revocation is another way to deal this issue where key for data access expires automatically. This solution rests in a very strong assumption of time determination in advance. In this paper we have proposed a mutable encryption for oblivious data access in cloud storage where the access key becomes ineffective after defined number of threshold by the data owner. The proposed solution adds to its novelty by introducing mutable encryption while accessing the data obliviously.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권11호
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• pp.2254-2271
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• 2011

Access control in dynamic environments needs the ability to provide more access opportunities of information to users, while also ensuring protection information from malicious users. Trust and risk are essential factors and can be combined together in access control decision-making to meet the above requirement. In this paper, we propose the combination of the trust and risk in access control to balance information accessibility and protection. Access control decision is made on the basis of trustworthiness of users and risk value of permissions. We use potential relations between users and relations between permissions in access control. Our approach not only provides more access opportunities for trustworthy users in accessing permissions, but also enforces traditional access control constraints such as Chinese Wall policy and Separation of Duty (SoD) of Role-Based Access Control (RBAC) model in an effective way.

• 정보교육학회논문지
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• 제1권2호
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• pp.57-66
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• 1997

The primary purpose of security mechanisms in a computer systems is to control the access to information. There are two types of access control mechanisms to be used typically. One is discretionary access control(DAC) and another is mandatory access control(MAC). In this study an access control mechanism is introduced for secure access path in security system. The security policy of this access control is that no disclosure of information and no unauthorized modification of information. To make this access control correspond to security policy, we introduce three properties; read, write and create.

• Journal of Communications and Networks
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• 제13권6호
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• pp.639-654
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• 2011

In this paper, we present a channel access mechanism, referred to as the enhanced mesh coordinated channel access (eMCCA) mechanism, for IEEE 802.11s-based wireless mesh networks. The current draft of IEEE 802.11s includes an optional medium access control (MAC), denoted as MCCA, which is designed to provide collision-free and guaranteed channel access during reserved periods. However, the MCCA mechanism fails to achieve the desired goal in the presence of contending non-MCCA nodes; this is because non-MCCA nodes are not aware of MCCA reservations and have equal access opportunities during reserved periods. We first present a probabilistic analysis that reveals the extent to which the performance of MCCA may be affected by contending non-MCCA nodes. We then propose eMCCA, which allows MCCA-enabled nodes to enjoy collision-free and guaranteed channel access during reserved periods by means of prioritized and preemptive access mechanisms. Finally, we evaluate the performance of eMCCA through extensive simulations under different network scenarios. The simulation results indicate that eMCCA outperforms other mechanisms in terms of success rate, network throughput, end-to-end delay, packet-loss rate, and mesh coordinated channel access opportunity-utilization.

• International Journal of Computer Science & Network Security
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• 제24권8호
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• pp.43-53
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• 2024

Access control systems are used to control the access of people to assets. In practice, assets are either tangible (e.g. goods, cash, etc.) or data. In order to handle tangible assets, a person must physically access the space in which the assets are located (e.g. a room or a building). Access control systems for this case have been known since antiquity and are based either on mechanical locks or on certificates. In the middle of the 20th century, systems based on electromagnetic phenomena appeared. In the second half of the same century, the need to control access to data also arose. And since data can also be accessed via a computer network, it was necessary to control not only the access of persons to areas with data storage, but also to control the electronic communication of persons with these storage facilities. The different types of the above systems have developed separately and more or less independently. This paper provides an overview of the current status of different types of systems, showing that these systems are converging technologically based on the use of electronics, computing and computer communication. Furthermore, the terminology and architecture of these systems is expanded in the article to allow a unified description of these systems. The article also describes the most common types of access control system configurations.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 ICEIC The International Conference on Electronics Informations and Communications
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• pp.165-169
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• 2004

This paper proposes a packet-based channel access scheme in Distributed-Queuing Request Update Multiple Access(DQRUMA) MAC(Media Access Control) protocol. To increase a channel access ratio, we eliminate the wait-to-transmit state that does not transmit Xmt_Req(Transmission Request) although the mobile terminal(MS) has new arrival packets in buffer.

• 디지털콘텐츠학회 논문지
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• 제13권3호
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• pp.335-342
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• 2012

이 연구의 목적은 지체 뇌병변장애인의 컴퓨터 접근성 향상을 도모하기 위하여 국내 최초 컴퓨터 접근 평가 시스템을 구현하는 것이다. 본 논문에 소개된 한국판 컴퓨터 접근 평가 시스템인 K-CAAS(Korea-Computer Access Assessment System) 소프트웨어는 클릭, 드래그, 메뉴 선택, 스캔, 스위치로 이루어진 다섯 가지 유형의 평가 기능을 가진다. 각각의 평가 기능 테스트는 사용자 개개인의 특성에 따라 구성 설정을 초급, 중급, 고급, 개별적으로 설정 할 수 있으며, 모든 테스트는 사용자의 수준 설정에 따라 기본 값을 가지고 사용자의 능력과 목표에 따라 난이도를 선택 및 조절할 수 있다. 테스트 시에 사용자의 훈련을 위해 임의로 선택할 수 있고, 사용자의 테스트 결과를 추적할 수 있다. 따라서, K-CAAS는 컴퓨터 접근성 평가, 뿐만 아니라 장애인의 컴퓨터 사용 능력 향상을 위한 재활 프로그램으로 사용이 가능하며 본 시스템을 통하여 향후 장애인의 컴퓨터 접근성이 향상되어 장애인이 스스로 컴퓨터 기능을 능숙하게 사용 할 수 있을 것을 기대한다.

• IEIE Transactions on Smart Processing and Computing
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• 제2권5호
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• pp.282-296
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• 2013

With the emergence of cloud computing, more and more sensitive user data are outsourced to remote storage servers. The privacy of users' access pattern to the data should be protected to prevent un-trusted storage servers from inferring users' private information or launching stealthy attacks. Meanwhile, the privacy protection schemes should be efficient as cloud users often use thin client devices to access the data. In this paper, we propose a lightweight scheme to protect the privacy of data access pattern. Comparing with existing state-of-the-art solutions, our scheme incurs less communication and computational overhead, requires significantly less storage space at the user side, while consuming similar storage space at the server. Rigorous proofs and extensive evaluations have been conducted to show that the proposed scheme can hide the data access pattern effectively in the long run after a reasonable number of accesses have been made.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권7호
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• pp.3339-3352
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• 2016

In ciphertext-policy attribute-based encryption (CP-ABE) scheme, a user's secret key is associated with a set of attributes, and the ciphertext is associated with an access policy. The user can decrypt the ciphertext if and only if the attribute set of his secret key satisfies the access policy specified in the ciphertext. In the present schemes, access policy is sent to the decryptor along with the ciphertext, which means that the privacy of the encryptor is revealed. In order to solve such problem, we propose a CP-ABE scheme with hidden access policy, which is able to preserve the privacy of the encryptor and decryptor. And what's more in the present schemes, the users need to do excessive calculation for decryption to check whether their attributes match the access policy specified in the ciphertext or not, which makes the users do useless computation if the attributes don't match the hidden access policy. In order to solve efficiency issue, our scheme adds a testing phase to avoid the unnecessary operation above before decryption. The computation cost for the testing phase is much less than the decryption computation so that the efficiency in our scheme is improved. Meanwhile, our new scheme is proved to be selectively secure against chosen-plaintext attack under DDH assumption.