Security Improvement on Wu and Zhu's Protocol for Password-Authenticated Group Key Exchange

Junghyun NAM  Juryon PAIK  Dongho WON  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E94-A   No.2   pp.865-868
Publication Date: 2011/02/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E94.A.865
Print ISSN: 0916-8508
Type of Manuscript: LETTER
Category: Cryptography and Information Security
group communication,  group key exchange,  password,  implicit key authentication,  key confirmation,  

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A group key exchange (GKE) protocol allows a group of parties communicating over a public network to establish a common secret key. As group-oriented applications gain popularity over the Internet, a number of GKE protocols have been suggested to provide those applications with a secure multicast channel. In this work, we investigate the security of Wu and Zhu's password-authenticated GKE protocol presented recently in FC'08. Wu and Zhu's protocol is efficient, supports dynamic groups, and can be constructed generically from any password-authenticated 2-party key exchange protocol. However, despite its attractive features, the Wu-Zhu protocol should not be adopted in its present form. Due to a flaw in its design, the Wu-Zhu protocol fails to achieve authenticated key exchange. We here report this security problem with the Wu-Zhu protocol and show how to solve it.