Secure Stateful Aggregation: A Practical Protocol with Applications in Differentially-Private Federated Learning

Fuente: arXiv
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Main Authors: Ball, Marshall, Bell-Clark, James, Gascon, Adria, Kairouz, Peter, Oh, Sewoong, Xie, Zhiye
Format: Preprint
Published: 2024
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author Ball, Marshall
Bell-Clark, James
Gascon, Adria
Kairouz, Peter
Oh, Sewoong
Xie, Zhiye
author_facet Ball, Marshall
Bell-Clark, James
Gascon, Adria
Kairouz, Peter
Oh, Sewoong
Xie, Zhiye
contents Recent advances in differentially private federated learning (DPFL) algorithms have found that using correlated noise across the rounds of federated learning (DP-FTRL) yields provably and empirically better accuracy than using independent noise (DP-SGD). While DP-SGD is well-suited to federated learning with a single untrusted central server using lightweight secure aggregation protocols, secure aggregation is not conducive to implementing modern DP-FTRL techniques without assuming a trusted central server. DP-FTRL based approaches have already seen widespread deployment in industry, albeit with a trusted central curator who provides and applies the correlated noise. To realize a fully private, single untrusted server DP-FTRL federated learning protocol, we introduce secure stateful aggregation: a simple append-only data structure that allows for the private storage of aggregate values and reading linear functions of the aggregates. Assuming Ring Learning with Errors, we provide a lightweight and scalable realization of this protocol for high-dimensional data in a new security/resource model, Federated MPC : where a powerful persistent server interacts with weak, ephemeral clients. We observe that secure stateful aggregation suffices for realizing DP-FTRL-based private federated learning: improving DPFL utility guarantees over the state of the art while maintaining privacy with an untrusted central party. Our approach has minimal overhead relative to existing techniques which do not yield comparable utility. The secure stateful aggregation primitive and the federated MPC paradigm may be of interest for other practical applications.
format Preprint
id arxiv_https___arxiv_org_abs_2410_11368
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Secure Stateful Aggregation: A Practical Protocol with Applications in Differentially-Private Federated Learning
Ball, Marshall
Bell-Clark, James
Gascon, Adria
Kairouz, Peter
Oh, Sewoong
Xie, Zhiye
Cryptography and Security
Recent advances in differentially private federated learning (DPFL) algorithms have found that using correlated noise across the rounds of federated learning (DP-FTRL) yields provably and empirically better accuracy than using independent noise (DP-SGD). While DP-SGD is well-suited to federated learning with a single untrusted central server using lightweight secure aggregation protocols, secure aggregation is not conducive to implementing modern DP-FTRL techniques without assuming a trusted central server. DP-FTRL based approaches have already seen widespread deployment in industry, albeit with a trusted central curator who provides and applies the correlated noise. To realize a fully private, single untrusted server DP-FTRL federated learning protocol, we introduce secure stateful aggregation: a simple append-only data structure that allows for the private storage of aggregate values and reading linear functions of the aggregates. Assuming Ring Learning with Errors, we provide a lightweight and scalable realization of this protocol for high-dimensional data in a new security/resource model, Federated MPC : where a powerful persistent server interacts with weak, ephemeral clients. We observe that secure stateful aggregation suffices for realizing DP-FTRL-based private federated learning: improving DPFL utility guarantees over the state of the art while maintaining privacy with an untrusted central party. Our approach has minimal overhead relative to existing techniques which do not yield comparable utility. The secure stateful aggregation primitive and the federated MPC paradigm may be of interest for other practical applications.
title Secure Stateful Aggregation: A Practical Protocol with Applications in Differentially-Private Federated Learning
topic Cryptography and Security
url https://arxiv.org/abs/2410.11368