• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.4
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• pp.11-27
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• 2005

To date, most identity-based key agreement protocols are based on a single PKG (Private Key Generator) environment. In 2002, Chen and Kudla proposed an identity-based key agreement protocol for a multiple PKG environment, where each PKG shares identical system parameters but possesses distinct master key. However, it is more realistic to assume that each PKG uses different system parameters including the PKG's master key. In this paper, we propose a new two party key agreement protocol between users belonging to different PKGs that do not share system parameters. We also extend this protocol to two types of tripartite key agreement protocols. We show that our two party protocol requires minimal amount of pairing computation for a multiple PKG environment and our tripartite protocol is more efficient than existing protocols. We also show that the proposed key agreement protocols satisfy every security requirements of key agreement protocol.

• Journal of Internet Computing and Services
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• v.7 no.3
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• pp.133-142
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• 2006

The purpose of the multiple key agreement protocol is to get efficiency in computational and communicational aspects compared to multiple executions of single key agreement protocol. However ID based tripartite multiple key agreement protocols have been proposed, it is reported that they can not resist unknown key-share attack or impersonation attack. How to design a secure and efficient ID-based authenticated tripartite multiple key agreement scheme to prevent all kinds of attacks remains an open problem. This paper proposes a multiple key agreement scheme combing the existing single key agreement protocol with a key derivation function. The proposed scheme can not only increase computational efficiency compared to the existing multiple key agreement protocol, but can ensure security of the proposed schemes by using a security proofed single key agreement protocol and key derivation function.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2002.11a
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• pp.77-80
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• 2002

그룹에 속한 멤버들만이 통신하고자 하는 그룹웨어 응용프로그램이 보안상 중요한 문제로 인식되면서, 그룹키를 안전하게 생성하여 나누어 갖는 것이 필요하게 되었다. 본 논문은 어떤 그룹에 속한 모든 멤버들이 잘 알려진 두 멤버간의 Diffie-Hellman의 키 교환 프로토콜을 이용하여, 모든 메시지들을 안전하게 전달함으로써 그룹키를 나누어 갖는 새로운 그룹키 동의 프로토콜을 제안한다. 이 프로토콜은 완전 이진 트리를 이용하여 기존의 많은 양의 모듈러 멱승 연산을 일부 곱셈 연산으로 전환함으로써, 그룹키를 만드는데 있이 모듈러 멱승 계산량을 줄이는데 효과적이다.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2006.06a
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• pp.322-325
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• 2006

그룹 키 동의 프로토콜에 관한 연구는 그동안 많은 연구자들에 의해 다양한 관점에서 진행되어왔으며, 최근 Nam 등이 유 무선 통합 네트워크 환경에서 효율적이면서도 안전한 그룹 키 동의 프로토콜을 제안하였다. 유 무선 통합 네트워크 환경에 적합한 그룹 키 동의 프로토콜을 설계하기 위해서는 고성능 연산 능력을 가진 유선 단말기의 특성과 상대적으로 계산능력이 떨어지는 무선 단말기의 특성이 함께 고려되어야 한다. 특히, 시스템자원의 제한성을 갖는 무선 단말기에서의 계산량을 최소화하는 문제는 그룹 키 동의 프로토콜 설계에 있어서 무엇보다 중요하다. 따라서, 본 논문에서는 무선 단말기의 계산량을 최소화하면서 유 무선 통합 네트워크 환경에 적합한 효율적인 그룹 키 동의 프로토콜을 제안하고자 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6C
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• pp.607-615
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• 2005

Group key agreement protocols are designed to allow a group of parties communicating over a public network to securely establish a common secret key. Over the years, a number of solutions to this problem have been proposed with varying degrees of complexity. However, there seems to have been no previous systematic look at the growing problem of key agreement over combined wired/wireless networks, consisting of both high-performance computing machines and low-power mobile devices. In this paper we present an efficient group key agreement scheme well suited for this networking environment. Our scheme meets efficiency, scalability, and all the desired security requirements.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.310-312
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• 2004

이동 애드혹 망은 기반구조가 없는, 즉, 고정된 라우터나 백본망 같은 기반구조가 없는 무선 이동 노드들로 구성된 망이다. 현재 이동 애드혹 망은 기반구조가 없어 보안이 가장 취약한 부분이다. 본 논문에서는 클러스터 구조 기반의 이동 애드혹 환경에서 안전하고 효율적인 방법으로 그룹의 세션키를 공유하는 패스워드 기반의 그룹키 동의 프로토콜을 제안한다. 그룹키 동의 프로토콜은 일련의 그룹을 형성하는 다수의 통신 참여자들이 공개된 통신망에서 안전하고 효율적인 방법으로 그룹의 세션키를 설정한다. 하지만 기존의 연구는 모두 상당한 양의 통신부하를 유발한다. 따라서 제안 프로토콜은 이동 애드혹 망에 적합한 대칭키 기반으로, 최적의 전송 메시지 복잡도와 2번의 통신 라운드를 요구하기 때문에 매우 효율적이다. 또한 그룹 구성원의 변경이 가능한 동적 특성과 전방향 안전성을 제공한다.

• Journal of KIISE:Information Networking
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• v.32 no.6
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• pp.651-658
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• 2005

Mobile communication has become more pervasive and it is considered as one of main concerns oi conferencing, multi-user games and etc. in mobile environment. These applications need to secure communication in group. Most of the published protocols are based on model which consists of a stationary base station and a cluster of mobile devices. In this paper, we have focused on the extended model of which participants are several base stations and mobile devices in different cells. We present a new group key protocol among mobile devices in different cells and analyze its security And we also look at how password authentication can be used to our group key agreement protocol. The mobile device's computing load may be reduced by using password authentication.

• The KIPS Transactions:PartC
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• v.11C no.3
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• pp.277-286
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• 2004

Password-based mechanism is widely used methods for user authentication. Password-based mechanisms are using memorable passwords(weak ferrets), therefore Password-based mechanism are vulnerable to the password guessing attack. To overcome this problem, man password-based authenticated key exchange protocols have been proposed to resist password guessing attacks. Recently, Seo-Sweeny proposed password-based Simple Authenticated Key Agreement(SAKA) protocol. In this paper, first, we will examine the SAKA and authenticated key agreement protocols, and then we will show that the proposed simple authenticated key agreement protocols are still insecure against Advanced Modification Attack. And we propose a password-based Simple Authenticated Key Agreement Protocol secure against Advanced Modification Attack.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.1
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• pp.23-33
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• 2006

Key Agreement protocols are among the most basic and widely used cryptographic protocols. In this paper we present an efficient O-based authenticated key agreement (AKA) protocol by using bilinear maps, especially well suited to unbalanced computing environments : an ID-based AKA protocol for Server and Client. Particularly, considering low-power clients' devices, we remove expensive operations such as bilinear maps from a client side. Our protocol uses signcryption and provide security in random oracle model.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.5
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• pp.105-112
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• 2003

In this raper, we propose two simple and efficient key agreement protocols, called SEKA-H and SEKA-E, which use a pre-shared password between two parties for mutual authentication and agreeing a common session key. The SEKA-H protocol uses a hash function to verify an agreed session key. The SEKA-E Protocol, a variant of SEKA-H, uses an exponentiation operation in the verification phase. They are secure against the man-in-the-middle attack the password guessing attack and the Denning-Sacco attack and provide the perfect forward secrecy. The SEKA-H protocol is very simple in structure and provides good efficiency compared with other well-known protocols. The SEKA-E protocol is also comparable with the previous protocols.