## Cryptology ePrint Archive: Report 2004/196

Password Based Key Exchange with Mutual Authentication

Shaoquan Jiang and Guang Gong

Abstract: A reasonably efficient password based key exchange (KE) protocol with provable security without random oracle was recently proposed by Katz, {\em et al.} \cite{KOY01} and later by Gennaro and Lindell \cite{GL03}. However, these protocols do not support mutual authentication (MA). The authors explained that this could be achieved by adding an additional flow. But then this protocol turns out to be 4-round. As it is known that a high entropy secret based key exchange protocol with MA\footnote{we do not consider a protocol with a time stamp or a stateful protocol (e.g., a counter based protocol). In other words, we only consider protocols in which a session execution within an entity is independent of its history, and in which the network is asynchronous.} is optimally 3-round (otherwise, at least one entity is not authenticated since a replay attack is applicable), it is quite interesting to ask whether such a protocol in the password setting (without random oracle) is achievable or not. In this paper, we provide an affirmative answer with an efficient construction in the common reference string (CRS) model. Our protocol is even simpler than that of Katz, {\em et al.} Furthermore, we show that our protocol is secure under the DDH assumption ({\em without} random oracle).

Category / Keywords: Protocol, Key Exchange, Password

Publication Info: An extended abstract appeared in SAC 2004. This is the full version.

Date: received 10 Aug 2004, last revised 14 Aug 2004

Contact author: jiangshq at calliope uwaterloo ca

Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation

Short URL: ia.cr/2004/196

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