Cryptology ePrint Archive: Report 2011/442
Another Look at Tightness
Sanjit Chatterjee and Alfred Menezes and Palash Sarkar
Abstract: We examine a natural, but non-tight, reductionist security proof for
deterministic message authentication code (MAC) schemes in the multi-user
setting. If security parameters for the MAC scheme are selected without
accounting for the non-tightness in the reduction, then the MAC scheme is
shown to provide a level of security that is less than desirable in the
multi-user setting. We find similar deficiencies in the security assurances
provided by non-tight proofs when we analyze some protocols in the
literature including ones for network authentication and aggregate MACs.
Our observations call into question the practical value of non-tight
reductionist security proofs. We also exhibit attacks on authenticated
encryption and disk encryption schemes in the multi-user setting.
Category / Keywords: cryptographic protocols /
Publication Info: Also available at http://anotherlook.ca
Date: received 14 Aug 2011, last revised 1 Apr 2013
Contact author: ajmeneze at uwaterloo ca
Available formats: PDF | BibTeX Citation
Note: Removed some inaccuracies in the description and analysis of Attack 1.
Version: 20130401:161011 (All versions of this report)
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