Cryptology ePrint Archive: Report 2005/265

Security Analysis of KEA Authenticated Key Exchange Protocol

Kristin Lauter and Anton Mityagin

Abstract: KEA is a Diffie-Hellman based key-exchange protocol developed by NSA which provides mutual authentication for the parties. It became publicly available in 1998 and since then it was neither attacked nor proved to be secure. We analyze the security of KEA and find that the original protocol is susceptible to a class of attacks. On the positive side, we present a simple modification of the protocol which makes KEA secure. We prove that the modified protocol, called KEA+, satisfies the strongest security requirements for authenticated key-exchange and that it retains some security even if a secret key of a party is leaked. Our security proof is in the random oracle model and uses the Gap Diffie-Hellman assumption. Finally, we show how to add a key confirmation feature to KEA+ (we call the version with key confirmation KEA+C) and discuss the security properties of KEA+C.

Category / Keywords: cryptographic protocols /

Publication Info: To appear at PKC 2006

Date: received 12 Aug 2005, last revised 16 Feb 2006

Contact author: amityagin at cd ucsd edu

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Version: 20060217:002157 (All versions of this report)

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