Preprint
Oct 2026
Reaction Attack on CKKS Deployments with Asymptotically Optimal Query Complexity
We study a protocol-level reaction leakage in CKKS deployments where public coefficient-to-slot (C2S) evaluation keys are combined with a client's 1-bit validity response. Under this deployment surface, a malicious evaluator can recover a ternary secret key using asymptotically optimal $O(H)$ reaction queries, where $H...
S. Bian, Hyeong-Soon Choe, Jiseung Kim et al.
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