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cs.CR2026
Privacy Amplification Without Independence: How Far Negative Dependence Carries the Guarantees of Poisson Subsampling
Xujun Che, Depeng Xu
Poisson subsampling is the default sampler in differentially private optimization because its independence makes privacy amplification tractable. Practical systems, however, are mo…
cs.CR2026
MoSign: Challenge-Response Motion-Watermark Authentication for Anonymous Virtual-Reality Users
Xujun Che, Thomas Carr, Depeng Xu +2
Social virtual reality (VR) creates a paradox. A user's body motion is a high-entropy biometric: head and hand trajectories alone re-identify users among tens of thousands with ove…
cs.CR2026
Memorization Is Not Extraction: Tight Differential-Privacy Bounds and Audit Blind Spots
Xujun Che, Depeng Xu, Shuhan Yuan
Memorization in large language models is measured through a zoo of definitions whose formal relations are unknown, and differential privacy (DP) is treated as a proxy against all o…