Reaction Attack on CKKS Deployments with Asymptotically Optimal Query Complexity

Reported by arXiv cs.CR (Song Bian, Hyeongmin Choe, Jiseung Kim, Changmin Lee)

Summary by Cyber Security News16 Oct 2026, 06:00 CET

About this summary. This is a short excerpt from the description that arXiv cs.CR published with its article. Cyber Security News did not report or verify the underlying story. Read the original: https://arxiv.org/abs/2610.21127

arXiv:2610.21127v1 Announce Type: new Abstract: 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 $H$ is the entropy of the secret key. The attack does not break RLWE or CKKS IND-CPA security.

Read the full article at arXiv cs.CR →

Source attribution: headline and facts are from arXiv cs.CR (arxiv.org). Summary method: excerpt of the source description. See our source attribution policy.

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