Cryptology ePrint Archive: Report 2009/392

Computational Soundness for Key Exchange Protocols with Symmetric Encryption

Ralf Kuesters and Max Tuengerthal

Abstract: Formal analysis of security protocols based on symbolic models has been very successful in finding flaws in published protocols and proving protocols secure, using automated tools. An important question is whether this kind of formal analysis implies security guarantees in the strong sense of modern cryptography. Initiated by the seminal work of Abadi and Rogaway, this question has been investigated and numerous positive results showing this so-called computational soundness of formal analysis have been obtained. However, for the case of active adversaries and protocols that use symmetric encryption computational soundness has remained a challenge.

In this paper, we show the first general computational soundness result for key exchange protocols with symmetric encryption, along the lines of a paper by Canetti and Herzog on protocols with public-key encryption. More specifically, we develop a symbolic, automatically checkable criterion, based on observational equivalence, and show that a key exchange protocol that satisfies this criterion realizes a key exchange functionality in the sense of universal composability. Our results hold under standard cryptographic assumptions.

Category / Keywords: cryptographic protocols / protocol analysis, computational soundness, simulation-based security

Publication Info: Abridged version appears in CCS 2009.

Date: received 11 Aug 2009

Contact author: tuengerthal at uni-trier de

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Version: 20090815:023716 (All versions of this report)

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