Partially Blinded Unlearning: Class Unlearning for Deep Networks from Bayesian Perspective

Abstract

To follow regulations on individual data privacy and safety, machine learning models must systematically remove information learned from specific subsets of a user's training data that can no longer be utilized. To address this problem, machine unlearning has emerged as an important area of research, that helps remove information learned from specific subsets of training data from a pre-trained model without needing to retrain the whole model from scratch. The principal aim of this study is to formulate a methodology aimed for the purposeful elimination of information linked to a specific class of data from a pre-trained classification network. This intentional removal decreases the model's performance specifically concerning the unlearned data class while simultaneously minimizing any detrimental impacts on the model's performance in other classes. To achieve this goal, we frame the class unlearning problem from a Bayesian perspective, which yields a loss function that minimizes the log-likelihood associated with the unlearned data with a stability regularization in parameter space. This stability regularization incorporates Mohalanobis distance with respect to the Fisher Information matrix and L2 distance from the pre-trained model parameters. Our novel approach, termed Partially-Blinded Unlearning (PBU), surpasses existing state-of-the-art class unlearning methods, demonstrating superior effectiveness. Notably, PBU achieves this efficacy without requiring information about the entire training dataset but only of the unlearned data points, marking a distinctive feature of its performance.