• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.316-319
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• 2011

그룹 키 협정 (Group key agreement)1)은 그룹 내의 노드 (member)가 하나의 비밀 키 (secret key)를 공유하도록 하는 프로토콜이다. 이 때, 그룹 키를 맺는 시간을 줄이기 위해 메시지의 수, 지수연산, 라운드 수가 적을수록 좋다. 그렇기 때문에 기존의 연구들에서는 이러한 요소들을 고려하여 프로토콜을 구성하였다. 하지만 그룹 내의 노드들이 계속 머무르는 상태에서 똑같은 그룹을 형성하는 것이 아니라 중간에 어떤 노드가 그룹을 떠나는 경우 (leave)도 있고 새로운 노드가 들어오는 경우 (join)도 있다. 또한, 그룹이 빠지는 경우 (group leave)도 있고, 그룹이 들어오는 경우 (group join)도 있다(Group Dynamics). 이러한 시나리오는 충분히 발생할 수 있기 때문에 이러한 요소들도 고려하여 프로토콜을 구성해야 한다. 그래서 이논문에서는 그룹 노드들의 join과 leave, 그룹들 간의 join, leave가 빈번한 경우도 고려하여 프로토콜을 제시할 것이다.

• Convergence Security Journal
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• v.16 no.7
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• pp.121-127
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• 2016

Recently, the popularity of smart devices such as Wi-Fi and LTE has increased the use ratio of wireless dramatically. On the other hand, the use ratio of wired internet is decreasing. The IoT(Internet of Things) is not only for people but also for communication between people and things, and communication between things and things by connecting to a wireless without choosing a place. Along with the rapid spread of the IoT there is a growing concern about the threat of IoT security. In this paper, the proposed scheme is a efficiency group key agreement in IoT environment that guarantees secure communication among light-weight devices. The proposed scheme securely be able to communication with the group devices who share a group key, generated by own secret value and the public value. Such property is suitable to the environment which are required a local area and a group.

• Journal of Korean Academy of Nursing
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• v.35 no.7
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• pp.1362-1370
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• 2005

Purpose: The purpose of this study was to identify the degree of attaining a smoking cessation goal when an agreement on means to achieve smoking cessation among male college student smokers was established. Method: This study was planned as a nonequivalent control group non-synchronized design and the sample was divided into an agreement group and a comparison group by convenience sampling in a college of G city. The data was analysed with SPSS Win10.0 using a Likelihood $x^2-test$, Odds ratio, Paired t-test and ANCOVA. Result: The theory that the degree of smoking cessation will be higher in the agreement group than the Comparison group was rejected (${\delta}$ = 2.567, p = .055). The theory that nicotine dependency will be lower in the agreement group than the comparison group was supported (F = 3.965, P = .049); however, the theory that the number of cigarettes smoked per day will be lower in the agreement group than the comparison group was rejected (F = 1.342, p = .252). Conclusion: It has been shown that an agreement on means to achieve smoking cessation goals is a key factor to success in quitting smoking.

• Journal of Communications and Networks
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• v.6 no.2
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• pp.156-162
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• 2004

In recent years, mobile ad-hoc networks have received a great deal of attention in both academia and industry to provide anytime-anywhere networking services. As wireless networks are rapidly deployed, the security of wireless environment will be mandatory. In this paper, we describe a group key management architecture and key agreement protocols for secure communication in mobile ad-hoc wireless networks (MANETs) overseen by unmanned aerial vehicles (UAVs). We use implicitly certified public keys method, which alleviates the certificate overhead and improves computational efficiency. The architecture uses a two-layered key management approach where the group of nodes is divided into: 1) Cell groups consisting of ground nodes and 2) control groups consisting of cell group managers. The chief benefit of this approach is that the effects of a membership change are restricted to the single cell group.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.3
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• pp.3-8
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• 2008

Ephemeral data are easily revealed if state specific information is stored in insecure memory or a random number generator is corrupted. In this letter, we show that Nam et al.'s group key agreement scheme, which is an improvement of Bresson et al.'s scheme, is not secure against session-state reveal attacks. We then propose an improvement to fix the security flaw.

• Journal of Convergence Society for SMB
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• v.4 no.4
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• pp.19-23
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• 2014

Group communication is becoming increasingly popular in Internet applications such as videoconferences, online chatting programs, games, and gambling. For secure communications, the integrity of messages, member authentication, and confidentiality must be provided among group members. To maintain message integrity, all group members use the Group Key (GK) for encrypting and decrypting messages while providing enough security to protect against passive attacks. Tree-based Group Diffie-Hellman (TGDH) is an efficient group key agreement protocol to generate the GK. TGDH assumes all members have an equal computing power. One of the characteristics of distributed computing and grid environments is heterogeneity; the member can be at a workstation, a laptop or even a mobile computer. Member reordering in the TDGH protocol could potentially lead to an improved protocol; such reordering should capture the heterogeneity of the network as well as latency. This research investigates dynamic reordering mechanisms to consider not only the overhead involved but also the scalability of the proposed protocol.

• The KIPS Transactions:PartC
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• v.12C no.2 s.98
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• pp.157-168
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• 2005

Group key agreement protocols are designed to provide a group of parties securely communicating over a public network with a session key. The mobile computing architecture is asymmetric in the sense of computational capabilities of participants. That is, the protocol participants consist of the stationary server(application servers) with sufficient computational Power and a cluster of mobile devices(clients) with limited computational resources. It is desirable to minimize the amount of computation performed by each group member in a group involving low-power mobile devices such as smart cards or personal digital assistants(PDAs). Furthermore we are required to update the group key with low computational costs when the members need to be excluded from the group or multiple new members need to be brought into an existing group. In this paper, we propose a dynamic group key protocol which offers computational efficiency to the clients with low-power mobile devices. We compare the total communicative and computational costs of our protocol with others and prove its suity against a passive adversary in the random oracle model.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.5
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• pp.25-34
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• 2009

Many conference systems over the Internet require authenticated group key agreement (AGKA) for secure and reliable communication. After Shamir [1] proposed the ID-based cryptosystem in 1984, ID-based AGKA protocols have been actively studied because of the simple public key management. In 2006, Zhou et al. [12] proposed two-round ID-based AGKA protocol which is very efficient in communication and computation complexity. However, their protocol does not provide user identification and suffers from the impersonation attack by malicious participants. In this paper, we propose improved ID-based AGKA protocol to prevent impersonation attack from Zhou et al.'s protocol. In our protocol, the malicious insider cannot impersonate another participants even if he knows the ephemeral group secret value. Moreover, our protocol reduces the computation cost from Zhou et al.'s protocol.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.9
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• pp.555-560
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• 2014

Recently, there are many researches on sharing group session key for members in a group. Among them, Harn and Lin proposed a scheme based on the Shamir's group session key and Liu, Cheng, Cao, and Jiang improved it to reduce the specific weakness. Especially, these schemes are based on the finite integer ring to protest the insider attack, in which a valid member can derived another member's secret using known information. In this paper, it is shown that the finite integer ring implies the failure of the reconstruction of group session key depending on the adopted parameters. We fix this problem and propose new group session key transfer scheme using the Shamir's secret sharing.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.2
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• pp.751-765
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• 2012

Key establishment protocols are fundamental for establishing secure communication channels over public insecure networks. Security must be given the topmost priority in the design of a key establishment protocol. In this work, we provide a security analysis on two recent key establishment protocols: Harn and Lin's group key transfer protocol and Dutta and Barua's group key agreement protocol. Our analysis shows that both the Harn-Lin protocol and the Dutta-Barua protocol have a flaw in their design and can be easily attacked. The attack we mount on the Harn-Lin protocol is a replay attack whereby a malicious user can obtain the long-term secrets of any other users. The Dutta-Barua protocol is vulnerable to an unknown key-share attack. For each of the two protocols, we present how to eliminate their security vulnerabilities. We also improve Dutta and Barua's proof of security to make it valid against unknown key share attacks.