• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.6
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• pp.312-332
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• 2008

Password-based authentication key exchange (PAKE) protocols in the literature typically assume a password that is shared between a client and a server. PAKE has been applied in various environments, especially in the “client-server” applications of remotely accessed systems, such as e-banking. With the rapid developments in modern communication environments, such as ad-hoc networks and ubiquitous computing, it is customary to construct a secure peer-to-peer channel, which is quite a different paradigm from existing paradigms. In such a peer-to-peer channel, it would be much more common for users to not share a password with others. In this paper, we consider password-based authentication key exchange in the three-party setting, where two users do not share a password between themselves but only with one server. The users make a session-key by using their different passwords with the help of the server. We propose an efficient password-based authentication key exchange protocol with different passwords that achieves forward secrecy in the standard model. The protocol requires parties to only memorize human-memorable passwords; all other information that is necessary to run the protocol is made public. The protocol is also light-weighted, i.e., it requires only three rounds and four modular exponentiations per user. In fact, this amount of computation and the number of rounds are comparable to the most efficient password-based authentication key exchange protocol in the random-oracle model. The dispensation of random oracles in the protocol does not require the security of any expensive signature schemes or zero-knowlegde proofs.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.4
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• pp.75-90
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• 2004

At Asiacrypt 2003, Shin et al., have proposed a new class for Authenticated Key Establishment (AKE) protocol named Leakage-Resilient AKE ${(LR-AKE)}^{[1]}$. The authenticity of LR-AKE is based on a user's password and his/her stored secrets in both client side and server side. In their LR-AKE protocol, no TRM(Tamper Resistant Modules) is required and leakage of the stored secrets from $.$my side does not reveal my critical information on the password. This property is useful when the following situation is considered :(1) Stored secrets may leak out ;(2) A user communicates with a lot of servers ;(3) A user remembers only one password. The other AKE protocols, such as SSL/TLS and SSH (based or PKI), Password-Authenticated Key Exchange (PAKE) and Threshold-PAKE (T-PAKE), do not satisfy that property under the above-mentioned situation since their stored secrets (or, verification data on password) in either the client or the servers contain enough information to succeed in retrieving the relatively short password with off-line exhaustive search. As of now, the LR-AKE protocol is the currently horn solution. In this paper, we prove its security of the LR-AKE protocol in the standard model. Our security analysis shows that the LR-AKE Protocol is provably secure under the assumptions that DDH (Decisional Diffie-Hellman) problem is hard and MACs are selectively unforgeable against partially chosen message attacks (which is a weaker notion than being existentially unforgeable against chosen message attacks).

• Journal of Internet Computing and Services
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• v.6 no.3
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• pp.17-30
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• 2005

A PAK(Password-Authenticated Key Exchange) protocol is used as a protocol to provide both the mutual authentication and allow the communication entities to share the session key for the subsequent secure communication, using the human-memorable portable short-length password, In this paper, we propose distributed key exchange protocols applicable to a smartcard using the MTI(Matsumoto, Takashima, Imai) key distribution protocol and PAK protocol. If only one server keeps the password verification data which is used for password authentication protocol. then It could easily be compromised by an attacker, called the server-compromised attack, which results in impersonating either a user or a server, Therefore, these password verification data should be distributed among the many server using the secret sharing scheme, The Object of this paper Is to present a password-based key exchange protocol which is to allow user authentication and session key distribution, using the private key in a smartcard and a password typed by a user. Moreover, to avoid the server-compromised attack, we propose the distributee key exchange protocols using the MTI key distribution protocol, And we present the security analysis of the proposed key exchange protocol and compare the proposed protocols with the existing protocols.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.6A
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• pp.179-183
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• 2008

Recently, an efficient password-authenticated key exchange protocol based on RSA has been proposed by Park et al. with formal security proof. In this letter, we analyze their protocol, and show that it is not secure against an active adversary who performs a dictionary attack. Moreover, we analyze the performance of the proposed attack and show that the attack is a threatening attack against the protocol.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.6
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• pp.113-124
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• 2002

Proposals for a password-based authenticated key exchange protocol that have been published so far almost concentrated on the provable security. But in a real environment such as mobile one, efficiency is a critical issue as security. In this paper we discuss the efficiency of PAK which is secure in the random oracle model ［l］. Among 4 hash functions in PAK the instantiation for $H_1$, which outputs a verifier of the password, has most important effect on the computational efficiency. We analyze two different methods for $H_1$ suggested in ［1］ and we show that $H_{lq}$ has merits in transforming to EC or XTR variants as well as in the efficiency. As an efficient variant. we propose PAK2-EC and PAK2-XTR which do not require any additional step converting a hash output into a point of elliptic curve or XTR subgroup when compared to the previous work on the PAK［2］. Finally we compare PAK2 with the password-based authenticated key exchange protocols such as SPEKE, SRP, and AMP.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.5
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• pp.23-36
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• 2004

This paper presents a password based authentication and key exchange protocol which can be used for both authenticating users and exchanging session keys for a subsequent secure communication over an untrusted network. Our idea is to increase a randomness of the password verification data, i.e., we split the password, and then amplify the split passwords in the high entropy-structured password verification data. And in order to prevent the verifier-compromised attack, we construct our system such that the password verification data is encrypted with the verifier's key and the private key of verifier used to encrypt it is stored in a secure place like a smart cards. Also we propose the distributed password authentication scheme utilizing many authentication servers in order to prevent the server-compromised attack occurred when only one server is used. Furthermore, the security analysis on the proposed protocol has been presented as a conclusion.

• Journal of Broadcast Engineering
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• v.13 no.2
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• pp.251-260
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• 2008

In this paper, we present two verifier-based multi-party PAKE (password-authenticated key exchange) protocols. The shared key can be used for secure content transmission. The suggested protocols are secure against server compromise attacks. Our first protocol is designed to provide forward secrecy and security against known-key attacks. The second protocol is designed to additionally provide key secrecy against the server which means that even the server can not know the session keys of the users of a group. The suggested protocols have a constant number of rounds are provably secure in the standard model. To the best of our knowledge, the proposed protocols are the first secure multi-party PAKE protocols against server compromise attacks in the literature.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.07a
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• pp.126-132
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• 2003

본 논문에서는 PAK(Password-Authenticated Key Exchange)와 PAK-R 프로토콜 기반으로 세가지 형태의 MTI(Matsumoto, Takashima, Imai) 키 일치 프로토콜을 적용하여, 안전한 보안성 요구 조건을 만족하면서 다양한 시스템에 적용할 수 있는, 패스워드-인증 키 분배 프로토콜을 소개하고자 한다. PAK 패스워드-인증 키 프로토콜은 통신 주체의 짧은 길이의 패스워드를 이용하여 통신 주체의 식별 및 상호 인증 후, 크기가 긴 세션키를 분배하기 위한 프로토콜이다. 또한 PAK는 이미 안전한 보안성이 증명되었고,［8,9,10］이를 이용한 많은 패스워드 기반의 인증 키 분배 프로토콜이 소개되었다. 본 논문은 이미 안정성 검증이 된 키 분배 프로토콜을 이용하여 새로운 PAK 프로토콜을 제안하며, credential의 이용성을 보장하기 위한 다양한 응용에 적용될 수 있다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.5
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• pp.73-92
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• 2005

Joux's tripartite key agreement protocol is one of the most prominent developments in the area of key agreement. Although certificate-based and ID-based authentication schemes have been proposed to provide authentication for Joux's protocol, no provably secure password-based one round tripartite key agreement protocol has been proposed yet. We propose a secure one round password-based tripartite key agreement protocol that builds on Joux's protocol and adapts PAK-EC scheme for password-based authentication, and present a proof of its security.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.2
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• pp.121-127
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• 2006

Recently, Chang et at.$^[9]$ proposed a new password-based key agreement protocol and a password change protocol to improve the efficiency in the password-based authenticated key agreement protocol proposed by Yeh et at.$^[8]$. However, Wang et al.$^[10]$ showed that their protected password change protocol is not secure under the denial of service attack and the dictionary attack This paper proposes an improved password change protocol to solve this problems in the Chang et al's protocol. In the proposed protocol, the format of communication messages is modified not to have any clue for the guessing of the password and verifying of the guessed password. The proposed protocol supports the advantages in the previous password-based protocols and solves the problems in them effectively.