Security

ALRED Blues: New Attacks on AES-Based MAC's

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Executive Summary

The ALRED family of Message Authentication Codes (MAC's) is based on three principles: Using a keyless block cipher in CBC mode to process the message, choosing AES-128 as this cipher, and reducing the effective number of rounds to 4 in order to speed up the processing. In this paper the authors show that each one of these principles creates significant weaknesses. More specifically, they show that any ALRED-type MAC which uses a keyless block cipher is vulnerable to new time/memory tradeoff attacks which are faster than generic tradeoff attacks on one-way functions.

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