• The KIPS Transactions:PartC
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• v.12C no.1 s.97
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• pp.29-36
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• 2005

A key agreement protocol is the most important part to establish a secure cryptographic system and the effort to standardize the key agreement protocols is in rapid progress. Several efficient and secure key agreement protocols have been proposed so far since Diffie-Hellman proposed a public key agreement system in 1976. But, since Diffie-Hellman based key agreement protocols need a lot of computation to establish the session key, they are not suitable for wireless Internet environment. In this paper, we propose the efficient key agreement protocol using Proxy server. The Proposed Protocol gives the security equivalent to that the Diffie-Hellman based Protocol and the computation work of mobile user can be decreased using proxy server.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1C
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• pp.117-123
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• 2008

We propose an improved Diffie-Hellman(DH) key agreement protocol over a radio link in peer-to-peer networks. The proposed protocol ensures a secure establishment of the shared key between two parties through distance bounding(DB). Proposed protocol is much improved in the sense that we now reduce the number of messages exchanged by two, the number of parameters maintained by four, and 2(7682(k/64)-64) of XOR operations, where k is the length of the random sequence used in the protocol. Also, it ensures a secure reusability of DH public parameters. Start after striking space key 2 times.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.07a
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• pp.47-50
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• 2003

본 논문에서는 DH(Diffie-Hellman) 기반의 사용자 인증 및 키 교환 프로토콜인 SAK(Simple Authentication and Key-agreement)를 제안하고자 한다. 제안 프로토콜 SAK는 단순하고 사용하기 쉬운 패스워드와 이산 대수 문제의 어려움을 이용하여 안전하고 효율적이다. 패스워드 기반 프로토콜의 취약점인 사전 공격(Dictionary attack)과 알려진 공격으로부터 안전하고 DH 기반의 기존 프로토콜보다 적은 지수 계산량을 요구한다.

• Communications of the Korean Mathematical Society
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• v.20 no.4
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• pp.849-859
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• 2005

We present a new identity based authenticated key agreement protocol from pairings satisfying the required security attributes. The security of our protocol is based on the bilinear Diffie- Hellman assumption.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.5
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• pp.115-124
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• 2005

We propose a new binding update(BU) protocol between mobile node(CN) and correspondent node(CN) for the purpose of preventing redirect attacks and DoS attacks observed from the existing BU protocols and enhancing the efficiency of the BU protocol. Home agent plays a role of both authentication server validating BU message and session key distribution center for MN and CN. Also propose the stateless Diffie-Hellman key agreement based on cryptographically generated address (CGA). Suity of our proposed Protocol is analyzed and compared with other protocols. The proposed protocol is more efficient than previous schemes in terms of the number of message flows and computation overhead and is secure against both redirect and DoS attacks.

• The Transactions of the Korea Information Processing Society
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• v.6 no.12
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• pp.3613-3621
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• 1999

In this paper, we analyzed the suity of key distribution protocol based on discrete logarithm for the purpose of designing key distribution protocol systematically. We also propose the efficient key agreement protocol with direct authentication. In comparison with Station-to-Station protocol, it provides the direct authentication using the Diffie-Hellman problem without signature.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.10a
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• pp.785-788
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• 2000

본 논문은 타원곡선 상에서 Diffie-Hellman 문제를 기반으로 하는 세 가지 키 합의 프로토콜을 제안한다. 먼저, MTI/AO, Unified/Model, MQV와 같은 기존의 키 합의 프로토콜들보다. 안전하고 효율적인 인증된 키 합의 프로토콜을 제안하고. 다음으로 메시지 인중 부호를 추가해서 3 회의 메시지로 이루어지는 키 공유 확인이 가능한 인증된 키 합의 프로토콜을 설계한다. 마지막으로 메시지 수는 2 회이면서 일방향으로 키 확인이 가능한 인증된 키 합의 프로토콜을 제안한다.

• Journal of the Korea Society of Computer and Information
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• v.23 no.2
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• pp.53-61
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• 2018

In this paper, the author proposes an efficient group key agreement scheme in a mobile environment where group members frequently join and leave. This protocol consists of basic protocols and general ones and is expected to be suitable for communications between a mobile device with limited computing capability and a key distributing center (or base station) with sufficient computing capability. Compared with other schemes, the performance of the proposed protocol is a bit more efficient in the aspects of the overall cost for both communication and computation where the computational efficiency of the scheme is achieved by using exclusive or operations and a one-way hash function. Also, in the aspect of security, it guarantees both forward and backward secrecy based on the computational Diffie-Hellman (CDH) assumption so that secure group communication can be made possible. Furthermore, the author proves its security against a passive adversary in the random oracle model.

• The KIPS Transactions:PartC
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• v.12C no.7 s.103
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• pp.949-958
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• 2005

In the paper we study key agreement schemes when a party needs to establish a session key with each of several parties, thus having multiple session keys. This situation can be represented by a graph, tailed a key graph, where a vertex represents a party and an edge represents a relation between two parties sharing a session key. graphs to establish all session keys corresponding to all edges in a key graph simultaneously in a single session. A key agreement protocol of a key graph is a natural extension of a two-party key agreement protocol. We propose a new key exchange model for key graphs which is an extension of a two-party key exchange model. using the so-called randomness re-use technique which re-uses random values to make session keys for different sessions, we suggest two efficient key agreement protocols for key graphs based on the decisional Diffie-Hellman assumption, and prove their securities in the key exchange model of key graphs. Our first scheme requires only a single round and provides key independence. Our second scheme requires two rounds and provides forward secrecy. Both are proven secure In the standard model. The suggested protocols are the first pairwise key agreement protocols and more efficient than a simple scheme which uses a two-party key exchange for each necessary key. Suppose that a user makes a session key with n other users, respectively. The simple scheme's computational cost and the length of the transmitted messages are increased by a factor of n. The suggested protocols's computational cost also depends on n, but the length of the transmitted messages are constant.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.3
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• pp.81-90
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• 2007

In the UMTS (Universal Mobile Telecommunication System), which is one of 3G mobile communication standards, the protocol called UMTS AKA (Authentication and Key Agreement) is used to authenticate mobile stations. However, the UMTS AKA protocol has some weakness, including network bandwidth consumption between a SN (Serving Network) and a HN (Home Network) and SQN (SeQuence Number) synchronization. In this paper, we propose a new improved protocol for UMTS that overcomes UMTS AKA weakness. Our protocol solves the privacy problem caused by IMSI (International Mobile Subscriber Identity)'s disclosure and provides perfect forward secrecy using ECDH (Elliptic Curve Diffie Hellman).