• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권12호
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• pp.5135-5149
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• 2015

Communications among multi-party must be fast, cost effective and secure. Today's computing environments such as internet conference, multi-user games and many more applications involve multi-party. All participants together establish a common session key to enable multi-party and secure exchange of messages. Multi-party password-based authenticated key exchange scheme allows users to communicate securely over an insecure network by using easy-to-remember password. Kwon et al. proposed a practical three-party password-based authenticated key exchange (3-PAKE) scheme to allow two users to establish a session key through a server without pre-sharing a password between users. However, Kwon et al.'s scheme cannot meet the security requirements of key authentication, key confirmation and anonymity. In this paper, we present a novel, simple and efficient multi-party password-based authenticated key exchange (M-PAKE) scheme based on the elliptic curve cryptography for mobile environment. Our proposed scheme only requires two round-messages. Furthermore, the proposed scheme not only satisfies security requirements for PAKE scheme but also achieves efficient computation and communication.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권12호
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• pp.3244-3260
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• 2013

A three-party password-based authenticated key exchange (PAKE) protocol allows two clients registered with a trusted server to generate a common cryptographic key from their individual passwords shared only with the server. A key requirement for three-party PAKE protocols is to prevent an adversary from mounting a dictionary attack. This requirement must be met even when the adversary is a malicious (registered) client who can set up normal protocol sessions with other clients. This work revisits three existing three-party PAKE protocols, namely, Guo et al.'s (2008) protocol, Huang's (2009) protocol, and Lee and Hwang's (2010) protocol, and demonstrates that these protocols are not secure against offline and/or (undetectable) online dictionary attacks in the presence of a malicious client. The offline dictionary attack we present against Guo et al.'s protocol also applies to other similar protocols including Lee and Hwang's protocol. We conclude with some suggestions on how to design a three-party PAKE protocol that is resistant against dictionary attacks.

• 한국산학기술학회논문지
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• 제10권2호
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• pp.388-395
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• 2009

2006년에 공개키 연산 대신 XOR 연산과 해쉬함수만을 사용하는 스마트카드를 이용하는 3자 참여 인증된 키 교환 프로토콜이 제안되었다. 최근에는 개인프라이버시에 대한 관심이 높아지며 사용자 익명성을 보호하기 위한 연구가 진행되고 있다. 본 논문에서는 2006년 제안된 3자 참여 인증된 키 교환 프로토콜이 사용자 익명성을 제공하지 못하며 잘못된 입력값 감지가 늦다는 문제점을 제기하고, 이러한 문제점을 해결하기 위해서 스마트카드 기반 3자 참여 키 교환 프로토콜을 제안하였다.

• 정보보호학회논문지
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• 제16권6호
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• pp.73-80
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• 2006

최근 Sun등은 서버의 공개키를 사용하고 사용자의 패스워드로부터 유도된 검증자를 이용한 3자 참여 인증된 키교환 프로토콜을 제안하였다. 본 논문에서는 스마트카드를 사용한 패스워드 기반의 3자 참여 인증된 키교환 프로토콜을 제안한다. 제안된 프로토콜은 Sun등의 프로토콜에 비해 공개키 연산 대신 XOR과 해쉬함수 연산을 사용하기 때문에 계산비용이 매우 작으며, 또한 메시지 전송회수도 20% 줄어들기 때문에 효율적으로 인증된 키 교환을 수행할 수 있다. 또한, 제안된 기법에서는 패스워드를 서버에 저장하지 않으므로 패스워드 추측공격에 안전하고, 두 사용자들 간에 공유된 세션키를 서버가 알 수 없기 때문에 서버 Compromise 공격으로부터도 안전하다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권5호
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• pp.1313-1327
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• 2013

How to make people keep both the confidentiality of the sensitive data and the privacy of their real identity in communication networks has been a hot topic in recent years. Researchers proposed privacy-preserving authenticated key exchange protocols (PPAKE) to answer this question. However, lots of PPAKE protocols need users to remember long secrets which are inconvenient for them. In this paper we propose a lightweight three-party privacy-preserving authentication key exchange (3PPAKE) protocol using smart card to address the problem. The advantages of the new 3PPAKE protocol are: 1. The only secrets that the users need to remember in the authentication are their short passwords; 2. Both of the users can negotiate a common key and keep their identity privacy, i.e., providing anonymity for both users in the communication; 3. It enjoys better performance in terms of computation cost and security. The security of the scheme is given in the random oracle model. To the best of our knowledge, the new protocol is the first provably secure authentication protocol which provides anonymity for both users in the three-party setting.

• 한국멀티미디어학회논문지
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• 제11권10호
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• pp.1403-1408
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• 2008

서버의 부담을 줄이기 위하여 스마트카드를 이용한 3자간 키 교환 프로토콜 방식과 패스워드 기반 2자간 키 교환 및 인증 프로토콜 방식들이 많이 제안되고 있다. 본 논문에서는 스마트 카드 기반 3자간 키 교환 및 인증 프로토콜 방식의 취약점에 대한 분석 및 검토를 행하였다. 또한, 심 경아 등에 의한 오프라인 패스워드 추측 공격에 취약점을 보인 곽 진 등의 방식을 분석하여 보고 이 공격에 대한 대책도 제시하고자 한다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.163-165
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• 2008

Recently, Lu and Cao proposed a password-authenticated key exchange protocol in the three party setting, and the authors claimed that their protocol works within three rounds. In this paper, we analyze the protocol and show the protocol cannot work within three rounds. We also find two security flaws in the protocol. The protocol is vulnerable to an undetectable password guessing attack and an off-line password guessing attack.

• 정보보호학회논문지
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• 제18권2호
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• pp.11-20
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• 2008

3자간 키 교환 프로토콜은 신뢰할 수 있는 서버의 도움을 받아 서버와 공유한 패스워드를 사용하여 사전에 특정 정보를 공유하지 않은 사용자와의 인증된 키 교환을 수행할 수 있는 암호학적 기법이다. 사용자는 다수의 패스워드를 기억하지 않고 서버와 공유한 패스워드만 기억하면 다수의 사용자와 키 교환이 가능하다. 서버는 사용자들의 키 교환 프로토콜이 수행될 때마다 두 사용자를 인증해주기 위한 통신과 연산을 수행한다. 따라서 동시에 다수의 사용자가 키 교환 프로토콜을 수행하면 서버에 큰 부담이 된다. 본 논문에서는 3자간 키 교환 프로토콜에서 실제 키 교환 수행 시 서버가 개입하지 않음으로서 서버의 부담을 최소화하는 프로토콜을 제안한다. 제안하는 프로토콜에서는 사용자의 등록 시에만 서버가 개입하고, 실제 키 교환 수행과정은 두 사용자들 사이에서만 이루어지므로 키 교환과정에서 서버는 연산이나 통신을 수행하지 않는다.

• 디지털산업정보학회논문지
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• 제5권4호
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• pp.139-150
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• 2009

Authentication and key exchange are fundamental for establishing secure communication channels over public insecure networks. Password-based protocols for authenticated key exchange are designed to work even when user authentication is done via the use of passwords drawn from a small known set of values. There have been many protocols proposed over the years for password authenticated key exchange in the three-party scenario, in which two clients attempt to establish a secret key interacting with one same authentication server. However, little has been done for password authenticated key exchange in the more general and realistic four-party setting, where two clients trying to establish a secret key are registered with different authentication servers. In fact, the recent protocol by Yeh and Sun seems to be the only password authenticated key exchange protocol in the four-party setting. But, the Yeh-Sun protocol adopts the so called "hybrid model", in which each client needs not only to remember a password shared with the server but also to store and manage the server's public key. In some sense, this hybrid approach obviates the reason for considering password authenticated protocols in the first place; it is difficult for humans to securely manage long cryptographic keys. In this work, we introduce a key agreement protocol and a key distribution protocol, respectively, that requires each client only to remember a password shared with its authentication server.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제2권6호
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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.