Information-Theoretic Decentralized Secure Aggregation with Passive Collusion Resilience

Fuente: arXiv
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Autores principales: Zhang, Xiang, Li, Zhou, Li, Shuangyang, Wan, Kai, Ng, Derrick Wing Kwan, Caire, Giuseppe
Formato: Preprint
Publicado: 2025
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author Zhang, Xiang
Li, Zhou
Li, Shuangyang
Wan, Kai
Ng, Derrick Wing Kwan
Caire, Giuseppe
author_facet Zhang, Xiang
Li, Zhou
Li, Shuangyang
Wan, Kai
Ng, Derrick Wing Kwan
Caire, Giuseppe
contents In decentralized federated learning (FL), multiple clients collaboratively learn a shared machine learning (ML) model by leveraging their privately held datasets distributed across the network, through interactive exchange of the intermediate model updates. To ensure data security, cryptographic techniques are commonly employed to protect model updates during aggregation. Despite growing interest in secure aggregation, existing works predominantly focus on protocol design and computational guarantees, with limited understanding of the fundamental information-theoretic limits of such systems. Moreover, optimal bounds on communication and key usage remain unknown in decentralized settings, where no central aggregator is available. Motivated by these gaps, we study the problem of decentralized secure aggregation (DSA) from an information-theoretic perspective. Specifically, we consider a network of $K$ fully-connected users, each holding a private input -- an abstraction of local training data -- who aim to securely compute the sum of all inputs. The security constraint requires that no user learns anything beyond the input sum, even when colluding with up to $T$ other users. We characterize the optimal rate region, which specifies the minimum achievable communication and secret key rates for DSA. In particular, we show that to securely compute one symbol of the desired input sum, each user must (i) transmit at least one symbol to others, (ii) hold at least one symbol of secret key, and (iii) all users must collectively hold no fewer than $K - 1$ independent key symbols. Our results establish the fundamental performance limits of DSA, providing insights for the design of provably secure and communication-efficient protocols in decentralized learning.
format Preprint
id arxiv_https___arxiv_org_abs_2508_00596
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publishDate 2025
record_format arxiv
spellingShingle Information-Theoretic Decentralized Secure Aggregation with Passive Collusion Resilience
Zhang, Xiang
Li, Zhou
Li, Shuangyang
Wan, Kai
Ng, Derrick Wing Kwan
Caire, Giuseppe
Information Theory
Cryptography and Security
Distributed, Parallel, and Cluster Computing
Machine Learning
In decentralized federated learning (FL), multiple clients collaboratively learn a shared machine learning (ML) model by leveraging their privately held datasets distributed across the network, through interactive exchange of the intermediate model updates. To ensure data security, cryptographic techniques are commonly employed to protect model updates during aggregation. Despite growing interest in secure aggregation, existing works predominantly focus on protocol design and computational guarantees, with limited understanding of the fundamental information-theoretic limits of such systems. Moreover, optimal bounds on communication and key usage remain unknown in decentralized settings, where no central aggregator is available. Motivated by these gaps, we study the problem of decentralized secure aggregation (DSA) from an information-theoretic perspective. Specifically, we consider a network of $K$ fully-connected users, each holding a private input -- an abstraction of local training data -- who aim to securely compute the sum of all inputs. The security constraint requires that no user learns anything beyond the input sum, even when colluding with up to $T$ other users. We characterize the optimal rate region, which specifies the minimum achievable communication and secret key rates for DSA. In particular, we show that to securely compute one symbol of the desired input sum, each user must (i) transmit at least one symbol to others, (ii) hold at least one symbol of secret key, and (iii) all users must collectively hold no fewer than $K - 1$ independent key symbols. Our results establish the fundamental performance limits of DSA, providing insights for the design of provably secure and communication-efficient protocols in decentralized learning.
title Information-Theoretic Decentralized Secure Aggregation with Passive Collusion Resilience
topic Information Theory
Cryptography and Security
Distributed, Parallel, and Cluster Computing
Machine Learning
url https://arxiv.org/abs/2508.00596