Hyperparameters in Score-Based Membership Inference Attacks

Fuente: arXiv
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Main Authors: Pradhan, Gauri, Jälkö, Joonas, Tobaben, Marlon, Honkela, Antti
Format: Preprint
Published: 2025
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author Pradhan, Gauri
Jälkö, Joonas
Tobaben, Marlon
Honkela, Antti
author_facet Pradhan, Gauri
Jälkö, Joonas
Tobaben, Marlon
Honkela, Antti
contents Membership Inference Attacks (MIAs) have emerged as a valuable framework for evaluating privacy leakage by machine learning models. Score-based MIAs are distinguished, in particular, by their ability to exploit the confidence scores that the model generates for particular inputs. Existing score-based MIAs implicitly assume that the adversary has access to the target model's hyperparameters, which can be used to train the shadow models for the attack. In this work, we demonstrate that the knowledge of target hyperparameters is not a prerequisite for MIA in the transfer learning setting. Based on this, we propose a novel approach to select the hyperparameters for training the shadow models for MIA when the attacker has no prior knowledge about them by matching the output distributions of target and shadow models. We demonstrate that using the new approach yields hyperparameters that lead to an attack near indistinguishable in performance from an attack that uses target hyperparameters to train the shadow models. Furthermore, we study the empirical privacy risk of unaccounted use of training data for hyperparameter optimization (HPO) in differentially private (DP) transfer learning. We find no statistically significant evidence that performing HPO using training data would increase vulnerability to MIA.
format Preprint
id arxiv_https___arxiv_org_abs_2502_06374
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Hyperparameters in Score-Based Membership Inference Attacks
Pradhan, Gauri
Jälkö, Joonas
Tobaben, Marlon
Honkela, Antti
Machine Learning
Artificial Intelligence
Membership Inference Attacks (MIAs) have emerged as a valuable framework for evaluating privacy leakage by machine learning models. Score-based MIAs are distinguished, in particular, by their ability to exploit the confidence scores that the model generates for particular inputs. Existing score-based MIAs implicitly assume that the adversary has access to the target model's hyperparameters, which can be used to train the shadow models for the attack. In this work, we demonstrate that the knowledge of target hyperparameters is not a prerequisite for MIA in the transfer learning setting. Based on this, we propose a novel approach to select the hyperparameters for training the shadow models for MIA when the attacker has no prior knowledge about them by matching the output distributions of target and shadow models. We demonstrate that using the new approach yields hyperparameters that lead to an attack near indistinguishable in performance from an attack that uses target hyperparameters to train the shadow models. Furthermore, we study the empirical privacy risk of unaccounted use of training data for hyperparameter optimization (HPO) in differentially private (DP) transfer learning. We find no statistically significant evidence that performing HPO using training data would increase vulnerability to MIA.
title Hyperparameters in Score-Based Membership Inference Attacks
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2502.06374