Privacy Amplification for Matrix Mechanisms

Fuente: arXiv
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Autori principali: Choquette-Choo, Christopher A., Ganesh, Arun, Steinke, Thomas, Thakurta, Abhradeep
Natura: Preprint
Pubblicazione: 2023
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author Choquette-Choo, Christopher A.
Ganesh, Arun
Steinke, Thomas
Thakurta, Abhradeep
author_facet Choquette-Choo, Christopher A.
Ganesh, Arun
Steinke, Thomas
Thakurta, Abhradeep
contents Privacy amplification exploits randomness in data selection to provide tighter differential privacy (DP) guarantees. This analysis is key to DP-SGD's success in machine learning, but, is not readily applicable to the newer state-of-the-art algorithms. This is because these algorithms, known as DP-FTRL, use the matrix mechanism to add correlated noise instead of independent noise as in DP-SGD. In this paper, we propose "MMCC", the first algorithm to analyze privacy amplification via sampling for any generic matrix mechanism. MMCC is nearly tight in that it approaches a lower bound as $ε\to0$. To analyze correlated outputs in MMCC, we prove that they can be analyzed as if they were independent, by conditioning them on prior outputs. Our "conditional composition theorem" has broad utility: we use it to show that the noise added to binary-tree-DP-FTRL can asymptotically match the noise added to DP-SGD with amplification. Our amplification algorithm also has practical empirical utility: we show it leads to significant improvement in the privacy-utility trade-offs for DP-FTRL algorithms on standard benchmarks.
format Preprint
id arxiv_https___arxiv_org_abs_2310_15526
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Privacy Amplification for Matrix Mechanisms
Choquette-Choo, Christopher A.
Ganesh, Arun
Steinke, Thomas
Thakurta, Abhradeep
Machine Learning
Cryptography and Security
Privacy amplification exploits randomness in data selection to provide tighter differential privacy (DP) guarantees. This analysis is key to DP-SGD's success in machine learning, but, is not readily applicable to the newer state-of-the-art algorithms. This is because these algorithms, known as DP-FTRL, use the matrix mechanism to add correlated noise instead of independent noise as in DP-SGD. In this paper, we propose "MMCC", the first algorithm to analyze privacy amplification via sampling for any generic matrix mechanism. MMCC is nearly tight in that it approaches a lower bound as $ε\to0$. To analyze correlated outputs in MMCC, we prove that they can be analyzed as if they were independent, by conditioning them on prior outputs. Our "conditional composition theorem" has broad utility: we use it to show that the noise added to binary-tree-DP-FTRL can asymptotically match the noise added to DP-SGD with amplification. Our amplification algorithm also has practical empirical utility: we show it leads to significant improvement in the privacy-utility trade-offs for DP-FTRL algorithms on standard benchmarks.
title Privacy Amplification for Matrix Mechanisms
topic Machine Learning
Cryptography and Security
url https://arxiv.org/abs/2310.15526