Better Gaussian Mechanism using Correlated Noise
- URL: http://arxiv.org/abs/2408.06853v2
- Date: Tue, 29 Oct 2024 14:58:32 GMT
- Title: Better Gaussian Mechanism using Correlated Noise
- Authors: Christian Janos Lebeda,
- Abstract summary: We show that adding a random variable distributed as a Gaussian with variance scaled by $(sqrtd + 1)/4$ to all counts allows us to reduce the variance of the independent noise samples to scale only with $(d + sqrtd)/4$.
The central idea of our mechanism is simple and the technique is flexible.
- Score: 1.450405446885067
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: We present a simple variant of the Gaussian mechanism for answering differentially private queries when the sensitivity space has a certain common structure. Our motivating problem is the fundamental task of answering $d$ counting queries under the add/remove neighboring relation. The standard Gaussian mechanism solves this task by adding noise distributed as a Gaussian with variance scaled by $d$ independently to each count. We show that adding a random variable distributed as a Gaussian with variance scaled by $(\sqrt{d} + 1)/4$ to all counts allows us to reduce the variance of the independent Gaussian noise samples to scale only with $(d + \sqrt{d})/4$. The total noise added to each counting query follows a Gaussian distribution with standard deviation scaled by $(\sqrt{d} + 1)/2$ rather than $\sqrt{d}$. The central idea of our mechanism is simple and the technique is flexible. We show that applying our technique to another problem gives similar improvements over the standard Gaussian mechanism.
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