[Resource Topic] 2022/1097: Post-Quantum Security of the (Tweakable) FX Construction, and Applications

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Post-Quantum Security of the (Tweakable) FX Construction, and Applications

Authors: Gorjan Alagic, Chen Bai, Jonathan Katz, Christian Majenz, Patrick Struck


The FX construction provides a way to increase the effective key length of a block cipher E. We prove security of a tweakable version of the FX construction in the post-quantum setting, i.e., against a quantum attacker given only classical access to the secretly keyed construction while retaining quantum access to E, a setting that seems to be the most relevant one for real-world applications. We then use our results to prove post-quantum security—in the same model—of the (plain) FX construction, Elephant (a finalist of NIST’s lightweight cryptography standardization effort), and Chaskey (an ISO-standardized lightweight MAC).

ePrint: https://eprint.iacr.org/2022/1097

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