arXiv Machine Learning

Minimax Gaussian Mechanisms for Continual Machine Unlearning

The paper introduces Gaussian mechanisms for Newton updates that enable continual machine unlearning—updating a model after record deletions without full retraining. Using Gaussian differential privacy and adaptive composition, it shows that the sequence of released models is statistically indistinguishable from exact retraining. The authors derive error bounds for the Newton approximation, calibrate independent and random‑walk Gaussian noise, and demonstrate minimax optimality under various residual and increment bounds, with empirical validation on simulations and credit‑default data.

arXiv Machine Learning
Oct 16

Differentially Private Distribution Release of Gaussian Mixture Models via KL-Divergence Minimization

The paper proposes a method for releasing Gaussian Mixture Models (GMMs) under differential privacy (DP) by minimizing Kullback‑Leibler (KL) divergence between the released and non‑private models. It jointly optimizes privacy‑budget allocation and parameter perturbations for mixture weights, means, and covariances, providing a tractable expression for KL divergence and a theoretical analysis of DP guarantees. Experiments on synthetic and real data show that the approach achieves strong privacy while preserving high utility.

By Hang Liu, Anna Scaglione, Sean Peisert
arXiv Machine Learning
Oct 8

Why Forget-Only Unlearning Needs Memorization

The paper investigates the feasibility of forget‑only unlearning, where a deletion algorithm can only access the trained model and the examples to forget, without any retained data or additional training information. It demonstrates that the possibility of successful unlearning depends on the learning method, showing that different datasets can yield identical models yet require distinct post‑deletion outputs. The authors establish lower bounds on the accuracy of unlearning relative to retraining and prove that, for certain learners, the algorithm must memorize a substantial portion of the training data—potentially the entire dataset—to handle arbitrary deletion requests, implying that models designed for forget‑only unlearning may need to retain more information than standard training does.

By Luka Radi\'c, Vikrant Singhal, Amartya Sanyal