• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.3
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• pp.727-733
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• 2008

An authentication between a user's terminal and a Access Control Router (ACR) is preceded so that a user receives secure WiBro services. Otherwise they can be exposed from many attack risks. So the Telecommunications Technology Association (TTA) constituted a mechanism of the mutual authentication for WiBro service. In mechanism a user executes the mutual authentication between a Portable Equipment (PE) and the ACR by using Portable Internet Subscriber Identity Module (PISIM). But this standard needs many message to authenticate the ACR and the users cann't use wireless Internet service. Therefore in this paper we propose the key agreement protocol between the PSS and the ACR to authenticate the PSS to ACR. At this time Power Support Device (PSD) fer supporting the calculated quantity of the PSS is participated in the key agreement protocol. The ACR sends a generated key to Key Authentication Server (KAS) via secure IPsec tunnel and then it preserves the identity of the PSS and the value of key after it enciphered them. In conclusion we analyze the security and efficiency of the proposed protocol.

• 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.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).

• IEMEK Journal of Embedded Systems and Applications
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• v.7 no.1
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• pp.53-59
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• 2012

Recently, LEE et al. proposed an attribute-based authenticated key agreement protocol over home network, which aimed to support authentication and key agreement between user and home server. However, if the home server is attacked in the protocol, the effects are influenced to the overall home network components severly. Thereby, this paper proposes a new ticket-based authentication protocol using user attributes between user and home devices to solve the problem. The proposed protocol supports the various levels of security to user by diversifying the network accessibility depending on user attribute. Thereby, the protocol could support more secure home network services.

• 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 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.14 no.4
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• pp.163-181
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• 2004

Group key agreement protocols are designed to solve the fundamental problem of securely establishing a session key among a group of parties communicating over a public channel. Although a number of protocols have been proposed to solve this problem over the years, they are not well suited for a high-delay wide area network; their communication overhead is significant in terms of the number of communication rounds or the number of exchanged messages, both of which are recognized as the dominant factors that slow down group key agreement over a networking environment with high communication latency. In this paper we present a communication-efficient group key agreement protocol and prove its security in the random oracle model under the factoring assumption. The proposed protocol provides perfect forward secrecy and requires only a constant number of communication rounds for my of group rekeying operations, while achieving optimal message complexity.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.6
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• pp.127-133
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• 2005

This paper presents a password-based key exchange protocol to guarantee secure communications for two users registered in a sever. In this protocol, the server is only responsible for the legality of the users but does not how the session key agreed between them. The protocol can resist the various attacks including server compromise attack and provide the perfect forward secrecy. The proposed protocol is efficient in terms of computation cost because of not employing the sewer's public key.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.518-520
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• 2003

This paper proposes a new session key agreement scheme which is based on Station-to-station protocol, or STS shortly. We extend key agreement model of STS, to take into account smart cards. Besides, we modify STS to withstand message replaying attack. Security analysis shows our scheme is still secure.

• 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.