• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.1
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• pp.5-21
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• 2008

In order to securely transmit multicast data packets in a mobile environment where frequent join/leave events are a characteristic of the environment, there is a need for a new secure and efficient group key management solution. We propose a secure group key generation/distribution solution providing scalability and reliability. Using this solution, when a mobile node, which is in a multicast session, enters a new domain, the agent of the domain joins the multicast session and coordinates its data packets with the mobile node. The agent encrypts and transmits subsequent data packets to the mobile node, using a local one-time pad key. This key is generated with FI sequences, enabling the mobile node to regenerate the same data packet, based on the information sent by the agent. Our performance analysis demonstrates that the proposed solution can significantly reduce the number of key generations and distributions, when it is applied to the hierarchical mobile IPv6 network.

• International Journal of Automotive Technology
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• v.8 no.3
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• pp.351-359
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• 2007

In this study, a hierarchical switching control scheme based on robust control theory is proposed for tracking control of vehicle longitudinal acceleration in the presence of large uncertainties. A model set consisting of four multiplicative-uncertainty models is set up, and its corresponding controller set is designed by the LMI approach, which can ensures the robust performance of the closed loop system under arbitray switching. Based on the model set and the controller set, a switching index function by estimating the system gain of the uncertainties between the plant and the nominal model is designed to determine when and which controller should be switched into the closed loop. After theoretical analyses, experiments have also been carried out to validate the proposed control algorithm. The results show that the control system has good performance of robust stability and tracking ability in the presence of large uncertainties. The response time is smaller than 1.5s and the max tracking error is about $0.05\;m/S^2$ with the step input.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.9
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• pp.3468-3495
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• 2015

In this paper, we present a multi-chain based hierarchical topology control algorithm (MCHTC) for wireless sensor networks. In this algorithm, the topology control process using static clustering is divided into sensing layer that is composed by sensor nodes and multi-hop data forwarding layer that is composed by leader nodes. The communication cost and residual energy of nodes are considered to organize nodes into a chain in each cluster, and leader nodes form a tree topology. Leader nodes are elected based on the residual energy and distance between themselves and the base station. Analysis and simulation results show that MCHTC outperforms LEACH, PEGASIS and IEEPB in terms of network lifetime, energy consumption and network energy balance.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.7 s.349
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• pp.14-23
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• 2006

Wireless Sensor Network(WSN) consists of huge number of sensor nodes which are small and inexpensive with very limited resources. The public key cryptography is undesirable to be used in WSN because of the limitations of the resources. A key management and predistribution techniques are required to apply the symmetric key cryptography in such a big network. Many key predistribution techniques and approaches have been proposed, but most of-them didn't consider the real WSN assumptions, In this paper, we propose a security framework that is based on a hierarchical grid for WSN considering the proper assumptions of the communication traffic and required connectivity. We apply simple keying material distribution scheme to measure the value of our framework. Finally, we provide security analysis for possible security threats in WSN.

• The Journal of Korean Association of Computer Education
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• v.3 no.1
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• pp.135-142
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• 2000

Recently the user of distance education system using Intemet-Web are increasing rapidly. This paper shows that Hierarchical WBI documents generator by using CGI is devised and applied to development of distance education system for group-level spoken english. This overcomes the problems of the ready-made programs, which took a lot of time and cost. To generate WBI documents, The key is established to each document saved in server by types of the hierarchical structure and is transmitted to client. By client transmitting this key to server when next documentary is required. Sever can know what documents the client needs. The WBI documentary generator tells the keys transmitted from the client, automatically generates a new documentary to send, and delivery it.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12C
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• pp.1288-1296
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• 2006

This paper proposes a fast authentication scheme based on hierarchical key structure (HiFA) for roaming mobile nodes in both intra-domain and inter-domain. The full authentication procedure standardized in IEEE 802.11 and 802.16 is difficult to be applied to a handover since it needs a heavy operation and long delay time during a handover. Though a number of schemes were proposed to solve the problem, the existing schemes might degrade the security of authentication or impose heavy administrative burden on the Pome authentication server. The main contribution of this paper is to reduce the communication and computation overhead of the home authentication sewer without degrading the security strength of the fast roaming authentication using hierarchical authentication key structure. The proposed scheme iii this paper decentralizes the administrative burden of the home authentication server to other network entities such as a local authentication server or access point and supports the security separation of the authentication key among local authentication servers using hash key chain.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.6
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• pp.93-103
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• 2005

As the usage of XML documents increases the requirement of security for XML documents is growing. Especially it is very important to solve the problem of access control to XML object which shares in the environment where various users connect to each others. In this paper, we propose the access control model and mechanism which is combined with role hierarchy in the RBAC and hierarchical key derivation/assign method for the access to XML object. So we implement the access control mechanism by including hierarchical key derivation method. The technique, we proposed, gives not only the benefit in management which RBAC provides in access control to XML objects, but also it ran help derive a lower layer key from the higher layer user's. This feature decrease the number of keys managed in each role hierarchy in comparison with previous methods.

• The Transactions of the Korea Information Processing Society
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• v.4 no.10
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• pp.2493-2500
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• 1997

We propose a new key management scheme for multiuser group which is classified as hierarchical structure (sometimes it is called a multilevel security hierarchy) in the symmetric key cryptosystem. The proposed scheme is based on the trapdoor one-way permutations which are generated by the pseudo-random permutation algorithm, and it is avaliable for multilevel hierarchical structure composed of a totally ordered set and a partially ordered set, since it has advantage for time and storage from an implemental point of view. Moreover, we obtain a performance analysis by comparing with the other scheme, and show that the proposed scheme is very efficient for computing time of key generation and memory size of key storage.

• Journal of Creative Information Culture
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• v.5 no.3
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• pp.345-353
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• 2019

Several studies have been proposed to improve storage space efficiency by expressing binary trie data structure as a linear binary bit string. Compact binary tree approach generated using one binary trie increases the key search time significantly as the binary bit string becomes very long as the size of the input key set increases. In order to reduce the key search range, a hierarchical compact binary tree technique that hierarchically expresses several small binary compact trees has been proposed. The search time increases proportionally with the number and length of binary bit streams. In this paper, we generate several binary compact trees represented by full binary tries hierarchically. The search performance is improved by allowing a path for the binary bit string corresponding to the search range to be determined through simple numeric conversion. Through the performance evaluation using the worst time and space complexity calculation, the proposed method showed the highest performance for retrieval and key insertion or deletion. In terms of space usage, the proposed method requires about 67% ~ 68% of space compared to the existing methods, showing the best space efficiency.

• Computers and Concrete
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• v.32 no.6
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• pp.567-576
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• 2023

In this study, a 3D microstructure-based model is established to simulate the effective thermal conductivity of cement paste, covering varying influencing factors associated with microstructure and thermal transfer mechanisms. The virtual cement paste divided into colloidal C-S-H and heterogeneous paste are reconstructed based on its structural attributes. Using the two-level hierarchical cement pastes as inputs, a lattice Boltzmann model for heat conduction is presented to predict the thermal conductivity. The results suggest that due to the Knudsen effect induced by the nanoscale pore, the thermal conductivity of air in C-S-H gel pore is significantly decreased, maximumly accounting for 3.3% thermal conductivity of air at the macroscale. In the cement paste, the thermal conductivities of dried and saturated cement pastes are stable at the curing age larger than 100 h. The high water-to-cement ratio can decrease the thermal conductivity of cement paste.