Continual Counting with Gradual Privacy Expiration

Fuente: arXiv
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Autores principales: Andersson, Joel Daniel, Henzinger, Monika, Pagh, Rasmus, Steiner, Teresa Anna, Upadhyay, Jalaj
Formato: Preprint
Publicado: 2024
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author Andersson, Joel Daniel
Henzinger, Monika
Pagh, Rasmus
Steiner, Teresa Anna
Upadhyay, Jalaj
author_facet Andersson, Joel Daniel
Henzinger, Monika
Pagh, Rasmus
Steiner, Teresa Anna
Upadhyay, Jalaj
contents Differential privacy with gradual expiration models the setting where data items arrive in a stream and at a given time $t$ the privacy loss guaranteed for a data item seen at time $(t-d)$ is $εg(d)$, where $g$ is a monotonically non-decreasing function. We study the fundamental $\textit{continual (binary) counting}$ problem where each data item consists of a bit, and the algorithm needs to output at each time step the sum of all the bits streamed so far. For a stream of length $T$ and privacy $\textit{without}$ expiration continual counting is possible with maximum (over all time steps) additive error $O(\log^2(T)/\varepsilon)$ and the best known lower bound is $Ω(\log(T)/\varepsilon)$; closing this gap is a challenging open problem. We show that the situation is very different for privacy with gradual expiration by giving upper and lower bounds for a large set of expiration functions $g$. Specifically, our algorithm achieves an additive error of $ O(\log(T)/ε)$ for a large set of privacy expiration functions. We also give a lower bound that shows that if $C$ is the additive error of any $ε$-DP algorithm for this problem, then the product of $C$ and the privacy expiration function after $2C$ steps must be $Ω(\log(T)/ε)$. Our algorithm matches this lower bound as its additive error is $O(\log(T)/ε)$, even when $g(2C) = O(1)$. Our empirical evaluation shows that we achieve a slowly growing privacy loss with significantly smaller empirical privacy loss for large values of $d$ than a natural baseline algorithm.
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id arxiv_https___arxiv_org_abs_2406_03802
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Continual Counting with Gradual Privacy Expiration
Andersson, Joel Daniel
Henzinger, Monika
Pagh, Rasmus
Steiner, Teresa Anna
Upadhyay, Jalaj
Cryptography and Security
Data Structures and Algorithms
Differential privacy with gradual expiration models the setting where data items arrive in a stream and at a given time $t$ the privacy loss guaranteed for a data item seen at time $(t-d)$ is $εg(d)$, where $g$ is a monotonically non-decreasing function. We study the fundamental $\textit{continual (binary) counting}$ problem where each data item consists of a bit, and the algorithm needs to output at each time step the sum of all the bits streamed so far. For a stream of length $T$ and privacy $\textit{without}$ expiration continual counting is possible with maximum (over all time steps) additive error $O(\log^2(T)/\varepsilon)$ and the best known lower bound is $Ω(\log(T)/\varepsilon)$; closing this gap is a challenging open problem. We show that the situation is very different for privacy with gradual expiration by giving upper and lower bounds for a large set of expiration functions $g$. Specifically, our algorithm achieves an additive error of $ O(\log(T)/ε)$ for a large set of privacy expiration functions. We also give a lower bound that shows that if $C$ is the additive error of any $ε$-DP algorithm for this problem, then the product of $C$ and the privacy expiration function after $2C$ steps must be $Ω(\log(T)/ε)$. Our algorithm matches this lower bound as its additive error is $O(\log(T)/ε)$, even when $g(2C) = O(1)$. Our empirical evaluation shows that we achieve a slowly growing privacy loss with significantly smaller empirical privacy loss for large values of $d$ than a natural baseline algorithm.
title Continual Counting with Gradual Privacy Expiration
topic Cryptography and Security
Data Structures and Algorithms
url https://arxiv.org/abs/2406.03802