Breaking and Repairing GCM Security Proofs

In this paper, the authors study the security proofs of GCM (Galois/Counter Mode of Operation). They first point out that a lemma, which is related to the upper bound on the probability of a counter collision, is invalid. Both the original privacy and authenticity proofs by the designers are based on the lemma. They further show that the observation can be translated into a distinguishing attack that invalidates the main part of the privacy proof. It turns out that the original security proofs of GCM contain a flaw, and hence the claimed security bounds are not justified. A very natural question is then whether the proofs can be repaired. They give an affirmative answer to the question by presenting new security bounds, both for privacy and authenticity.

Provided by: Nagoya University Topic: Security Date Added: Aug 2012 Format: PDF

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