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With the development of information technology, wireless communication, cloud computing, sensors, active research in big data, etc., everything of physical world is connected by the Internet. This new paradigm is called the Internet of Things (IoT). It's key to design and build that all electrical devices are connected, shared data and information, and provide suitable services for users in various domains through connected Internet.
To realize information collection and sharing data, and to provide a variety of useful services, devices, systems, or platforms in IoT environment require solving various security issues. Especially, access control has to be performed dynamic for supporting suitable services to users because users’ access permission is affected by contexts. The context is information produced in the diverse sensors, and such information provides various services through an intersystem information exchange in various domains and interaction. Such context is volatile information strongly influenced by environmental elements, such as time and space. Therefore, this dissertation focuses on the dynamic access control for IoT environment based on context. For context-based access control in IoT, the access permission technique that uses context is being intensely investigated because of the ease with which various dynamic access permissions can be assigned in accordance with the various changes in context. 
In this dissertation, we propose a model for context-based dynamic access control that uses intuitive 5W1H for the IoT called the IoT-CBDAC. According to this thesis, access permission is assigned dynamically according to the change in context information such that even for a subject with the same role, access permission is defined differently depending on the context information and access condition. The proposed model not only authorizes access based on roles, which is the key concept of RBAC, but dynamic access control is also possible because access permission is assigned based on context information, access condition, and intended goal. 
As a result, this dissertation address to present a comprehensive approach of dynamic access controls management. Also, this dissertation guarantees privacy protection when processing the context information in various domains, and assigns access permission without any limitation to certain domains. 

ABSTRACT	i

1. Introduction	1
1.1 Motivation and Purpose of the Research	1
1.2 Taxonomy	6
1.3 Organization of the Dissertation	7

2. Backgrounds and Related Works	9
2.1 Backgrounds	9
2.1.1 Discretionary Access Control (DAC)	9
2.1.2 Mandatory Access Control (MAC)	10
2.1.3 Role-based Access Control (RBAC)	10
2.2 Related Works	11
2.2.1 Purpose-based Access Control Models	11
2.2.2 Context-based Access Control Models	14
2.2.3 Ontology-based Context-Aware Models	17

3. Proposed Model	22
3.1 Dynamic Access Control Model	22
3.1.1 Ontological Context-Aware Model	25
3.1.2 Dynamic Access Control for Dynamic Access Permission	29
3.2 Mapping CA5W1HOnto and Access Condition	32
3.3 Dynamic Access Decision	35

4. Implementation and Experiment	39
4.1 Experiment	39
4.2 Implementation	42

5. Performance Evaluation	51
5.1 Quantitative Evaluation	51
5.1.1 Comparison between Domain Dependent Models and Our Approach for Adding New Domain	53
5.1.2 Comparison between Domain Dependent Models and Our Approach for Access Decision Time	55
5.1.3 Comparison between Context-based Models and Our Approach for Access Decision Time	57
5.2 Qualitative Evaluation	60

6. Conclusion and Future Works	63
6.1 Conclusion	63
6.2 Future Works	65

Bibliography	66

Appendix A.	73

Appendix B.	85

Abstaract (Korean)	95