• The KIPS Transactions:PartC
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• v.9C no.6
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• pp.799-808
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• 2002

According to the wide-spread of information transmission system over network, the use of cryptographic system to provide the integrity of transmitted message over network is increasing and the importance of that is emphasized. Because the security of the cryptographic system totally relies on the key, key management is a essential part of cryptographic system. A number of key agreement protocols have been proposed to far, but their rigorous security analysis is still open. In this paper, we analyze the features of Diffie-Hellman based standard key agreement protocols and provide the security analysis of those protocols against several kinds of active attacks.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.5
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• pp.37-43
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• 2002

This paper proposes a password-based mutual authentication and key agreement protocol, which is designed by applying ECDSA and ECDH. The proposed protocol, AKE-ECC, computes 2 times of point multiplication over ECC on each of client and server, and generates the key pairs(public key. private key) and a common session key using ECDH that is different compare to previously proposed protocol. It is against common attacks include a dictionary attack and the security of proposed protocol is based on the ECDLP, ECDH.

• Journal of information and communication convergence engineering
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• v.7 no.3
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• pp.340-344
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• 2009

Multi-server password authentication schemes enable remote users to obtain service from multiple servers with single password without separately registering to each server. In 2007, Hu-Niu-Yang proposed an improved efficient password authenticated key agreement scheme for multi-server architecture based on Chang-Lee's scheme proposed in 2004. This scheme is claimed to be more efficient and is able to overcome a few existing deficiencies in Chang-Lee's scheme. However, we find false claim of forward secrecy property and some potential threats such as offline dictionary attack, key-compromise attack, and poor reparability in their scheme. In this paper, we will discuss these issues in depth.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.4
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• pp.627-634
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• 2010

In this paper we suggest a group key agreement protocol among a group consisting more than 3 PKIs. From an 128 bit message, we produce a group key to any length size using a hash function. With a computer experiment we found that PKI's encryption/decryption time is the most dominant part of this procedure and an 160 bit ECC PKI is the most efficient system for distributing an 128 bit message in practical level. We implement this procedure over an unsecure multi user chatting system which is an open software. And we also show that this suggestion could be practically used in military business without a hardware implementation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.8
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• pp.4025-4042
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• 2017

Session initiation protocol (SIP) is a kind of powerful and common protocols applied for the voice over internet protocol. The security and efficiency are two urgent requirements and admired properties of SIP. Recently, Hamed et al. proposed an efficient authentication and key agreement scheme for SIP. However, we demonstrate that Hamed et al.'s scheme is vulnerable to de-synchronization attack and cannot provide anonymity for users. Furthermore, we propose an improved and efficient authentication and key agreement scheme by using elliptic curve cryptosystem. Besides, we prove that the proposed scheme is provably secure by using secure formal proof based on Burrows-Abadi-Needham logic. The comparison with the relevant schemes shows that our proposed scheme has lower computation costs and can provide stronger security.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.1
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• pp.119-131
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• 2013

With the explosive growth of computer networks, many remote service providing servers and multi-server network architecture are provided and it is extremely inconvenient for users to remember numerous different identities and passwords. Therefore, it is important to provide a mechanism for a remote user to use single identity and password to access multi-server network architecture without repetitive registration and various multi-server authentication schemes have been proposed in recent years. Recently, Tsaur et al. proposed an efficient and secure smart card based user authentication and key agreement scheme for multi-server environments. They claimed that their scheme satisfies all of the requirements needed for achieving secure password authentication in multi-server environments and gives the formal proof on the execution of the proposed authenticated key agreement scheme. However, we find that Tsaur et al.'s scheme is still vulnerable to impersonation attack and many logged-in users' attack. We propose an extended scheme that not only removes the aforementioned weaknesses on their scheme but also achieves user anonymity for hiding login user's real identity. Compared with other previous related schemes, our proposed scheme keeps the efficiency and security and is more suitable for the practical applications.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.4
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• pp.1779-1798
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• 2018

Heterogeneous wireless sensor networks (HEWSN) is a kind of wireless sensor networks (WSN), each sensor may has different attributes, HEWSN has been widely used in many aspects. Due to sensors are deployed in unattended environments and its resource constrained feature, the design of security and efficiency balanced authentication scheme for HEWSN becomes a vital challenge. In this paper, we propose a secure and lightweight user authentication and key agreement scheme based on biometric for HEWSN. Firstly, fuzzy extractor is adopted to handle the user's biometric information. Secondly, we achieve mutual authentication and key agreement among three entities, which are user, gateway and cluster head in the four phases. Finally, formal security analysis shows that the proposed scheme defends against various security pitfalls. Additionally, comparison results with other surviving relevant schemes show that our scheme is more efficient in term of computational cost, communication cost and estimated time. Therefore, the proposed scheme is well suitable for practical application in HEWSN.

• 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.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.7
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• pp.3678-3698
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• 2017

With the rapid development of vehicular ad hoc Network (VANET), it has gained significant popularity and received increasing attentions from both academics and industry communities in aspects of security and efficiency. To address the security and efficiency issues, a self-authentication and deniable efficient group key agreement protocol is proposed in this paper. The scheme establishes a group between road side units (RSUs) and vehicles by using self-authentication without certification authority, and improves certification efficiency by using group key (GK) transmission method. At the same time, to avoid the attacker attacking the legal vehicle by RSUs, we adopt deniable group key agreement method to negotiation session key (sk) and use it to transmit GK between RSUs. In addition, vehicles not only broadcast messages to other vehicles, but also communicate with other members in the same group. Therefore, group communication is necessary in VANET. Finally, the performance analysis shows superiority of our scheme in security problems, meanwhile the verification delay, transmission overheard and message delay get significant improvement than other related schemes.

• 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.