On the Concrete Security of Approximate FHE with Noise-Flooding Countermeasures

ePrint Report: On the Concrete Security of Approximate FHE with Noise-Flooding Countermeasures

Flavio Bergamaschi, Anamaria Costache, Dana Dachman-Soled, Hunter Kippen, Lucas LaBuff, Rui Tang

Approximate fully homomorphic encryption (FHE) schemes such as the CKKS scheme (Asiacrypt '17) are popular in practice due to their efficiency and utility for machine learning applications. Unfortunately, Li and Micciancio (Eurocrypt, '21) showed that, while achieving standard semantic (or $\mathsf{IND}\mbox{-}\mathsf{CPA}$ security), the CKKS scheme is broken under a variant security notion known as $\mathsf{IND}\mbox{-}\mathsf{CPA}^D$. Subsequently, …

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