• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.1
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• pp.8-14
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• 2003

In this paper, we investigate a rekey mechanism for a secure multicast group communications and relate the mechanism to the loss of information from group key exposal. We also combine cost for the information loss and cost for group key updates and analyze the optimum rekey interval. Using the results of the analysis in this paper, we can manage a secure multicast group efficiently with the minimal cost on the bases of number of group members, each member's security level and withdrawal rates.

• Journal of Industrial Technology
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• v.21 no.A
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• pp.123-127
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• 2001

This paper proposed for allotment of group key's rekey interval required from secure multicast environment. New group key distribution occurs in two cases: one is periodical update and the other is permitted or unpermitted withdrawal of group member. In later case, the group controller distributes new group key to member except withdrawal member because it can't predict precisely. In former case, the group member who cheated the group can adjust the rekey interval. Using relation between security level, overhead and cost from rekey interval, this paper suggests effective rekey interval allotment through probable performance analysis in large dynamic group.

• The Journal of Korean Association of Computer Education
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• v.7 no.1
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• pp.55-66
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• 2004

The Internet today provides group communication model, multicast service. It is important to keep security for multicast communication. Member leaving is associated with scalability problem for group key management. If one member of the group is removed, new group key has to be changed and communicated to all remaining members of group. Modification and distribution of new group keys for rekeying is an expensive operation. Minimizing the number of messages and operation cost for generation of the composite keys are important evaluating criteria of multicast key management scheme. Periodic rekey helps reducing these important parameters rather than removing members sequentially in fashion one after another. In this paper, Hamming distance is calculated between every members to be removed. The members with Hamming distance less than threshold are selected for rekeying procedure. With running the round assignment algorithm, our model has advantages of reducing the number of message and operation cost for generation of the composite keys for rekeying.

• Journal of KIISE:Information Networking
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• v.29 no.5
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• pp.583-594
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• 2002

Assuring the security of group communications such as tole-conference and software distribution requires a common group key be shared among the legal members in a secure manner. Especially for large groups with frequent membership change, efficient rekey mechanism is essential for scalability. One of the most popular ways to provide sealable rekey is to partition the group into several subgroups. In this paper, we propose a two-layered key management scheme which combines DEP and CBT, a protocol in which subgroup manager cannot access the multicast data and another that has a multi-core, respectively. We also select sub-group key management protocols suitable for our structure and design new rekey protocols to exclude the subgroup managers from the multicast data. Compared to previous protocols based on CBT, our scheme provides forward secrecy, backward secrecy and scalability. This would reduce the number of encryption and decryption for a rekey message and would improve the efficiency number of rekey messages and the amount of information related to group members that group managers must maintain compared to DEP.

• The KIPS Transactions:PartC
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• v.11C no.4
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• pp.409-418
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• 2004

Multicast services are provided on the Internet in fast increasing . Therefore it is important to keep security for multicast communication. Member leaving is deeply associated with scalability problem for group key management. If one member of the group is removed, new group key has to be generated and distributed to all remaining members of group. Minimizing the number of messages and operation cost for generation of the composite keys are important evaluating criteria of multicast key management scheme since generation and distribution of new keys for rekeying require expensive operation. Batch removal can reduce these important parameters rather than removing members sequentially In fashion one after another. In this paper, Hamming distance is calculated between eve교 members to be removed. The members with Hamming distance less than threshold are selected for rekeying procedure. With running the round assignment algorithm In the case of removing several members simultaneously, our model has advantages of reducing the number of message and operation cost for generation of the composite keys and eliminating possibility of collusion attack for rekeying.

• The Journal of Korean Association of Computer Education
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• v.9 no.2
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• pp.111-124
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• 2006

Multicast services are provided on the Internet in fast increasing. Therefore it is important to keep security for multicast communication. If a member of the group is removed, new group key has to be generated and distributed to all remaining members of group. Minimizing number of messages and operation cost for generation of the composite keys to be used to encrypting group key are important evaluating criteria of multicast key management scheme since generation and distribution of new keys for rekeying require expensive operation. Periodic batch rekeying can reduce these important parameters rather than rekeying sequentially in fashion one after another. In this paper, Hamming distance is calculated between every members to be removed. In batch rekeying the members with Hamming distance less than threshold are selected for rekeying procedure. With running the round assignment algorithm in the case of removing several members simultaneously, our scheme has advantages of reducing messages and operation cost for generation of the composite keys and eliminating possibility of collusion attack for rekeying. We evaluate performance of round assignment algorithm through simulation and show that our scheme is excellent after performance comparison of existent schemes and our scheme.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.292-294
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• 2001

멀티캐스트 정보보호 기술은 순수만 멀티캐스트 기술을 실용화 하는데 있어서 없어서는 안될 기술이다. 멀티캐스트 정보보호 기술에서 이슈가 되는 것은 여러 가지가 있으나, 본 논문에서는 인증된 수신자만이 데이터를 볼 수 있도록 하기 위해 필요한 키의 분배 및 rekey 연산에 대해 제안된 몇 가지 기술을 알아보고. 무선환경에서도 확장성을 제공할 수 있는 방안으로 기존의 OFT(One-way Function Tree) 메커니즘을 토대로 하는 WOFT(Mobile OFT) 메커니즘을 제안하고 제안하는 MOFT 메커니즘의 효율성을 분석한다.

• Journal of KIISE:Information Networking
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• v.37 no.5
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• pp.327-338
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• 2010

Complete Subtree scheme(CS) is a well known broadcast encryption scheme to perform group rekeying in a stateless manner. However, statelessness comes at a cost in terms of storage and message overhead in transmitting key material. We propose a Merged Complete Subtree scheme(MCS) to reduce the communication overhead. It is more practical to make broadcast encryption schemes in network environments with limited bandwidth resources. We define all possible subset unions for ever two subsets of CS as new subsets having own key. The modification causes more storage overhead. Nevertheless, it is possible to make the size of a header, including key materials, half using subset unions of MCS, because the size of a header depends on the number of used subsets. Our evaluation therefore shows that the proposed scheme significantly improves the communication overhead of CS, reducing by half the rekey communication cost. The proposed scheme has the advantage of rekey communication cost when the number of revoked users is significant percentage of the number of potential users. The proposed scheme is fully collusion resistant.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.21 no.3
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• pp.75-88
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• 2011

Messages need to transmit to the neighbors securely in wireless sensor network, because a sensor node is deployed in hostile area. Thus it is necessary to support secure communication. One of the most important communication part is secure multicast. Especially, group rekeying is a big problem for multicast key management. So, group rekeying must be proceed securely when secrete information is exposed by attacker. Many group rekeying schemes have been studied for ad hoc networks. However, these schemes are Ill1desirable in WSNs. In this paper, we proposed a novel group rekeying scheme in WSNs that it has very powerful security.

• The KIPS Transactions:PartB
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• v.9B no.5
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• pp.587-598
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• 2002

In multicast environment, the main objective of group key management is to provide security services to group communications by sharing a single group key among all the members of the group and subsequently encrypting and decrypting all the communication messages exchanged among the members of the group. Up to now, there has been no effort to develop group key management mechanism that considers the rate of users' join/leave operations. Hence, in this research, we propose group key management mechanisms that consider the rate of user's join/leave operations. We also define a new tree structure called variable tree which is much more flexible than full regular trees and show that variable trees are more efficient than full regular trees for group key management. Especially, we propose an algorithm that minimizes the necessary number of rekey messages according to the rate of join and leave operations. We also shows that if the rate of leave operation is greater than 50%, then the tree structure with degrees 2 or 3 are the optimal structures.