Cryptology ePrint Archive: Report 2013/248

Another Look at Security Theorems for 1-Key Nested MACs

Neal Koblitz and Alfred Menezes

Abstract: We prove a security theorem without collision-resistance for a class of 1-key hash-function-based MAC schemes that includes HMAC and Envelope MAC. The proof has some advantages over earlier proofs: it is in the uniform model, it uses a weaker related-key assumption, and it covers a broad class of MACs in a single theorem. However, we also explain why our theorem is of doubtful value in assessing the real-world security of these MAC schemes. In addition, we prove a theorem assuming collision-resistance. From these two theorems we conclude that from a provable security standpoint there is little reason to prefer HMAC to Envelope MAC or similar schemes.

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Date: received 1 May 2013, last revised 24 Dec 2013

Contact author: ajmeneze at uwaterloo ca

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Version: 20131224:202045 (All versions of this report)

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