BlockDFL: A Blockchain-based Fully Decentralized Peer-to-Peer Federated Learning Framework

TL;DR

BlockDFL is a blockchain-based decentralized federated learning framework that enhances security against poisoning attacks, reduces communication costs, and maintains high accuracy even with many malicious participants.

Contribution

It introduces a novel blockchain-based P2P federated learning framework with a voting and scoring mechanism for secure, efficient, and scalable decentralized training.

Findings

Achieves competitive accuracy with centralized FL.

Effectively defends against poisoning attacks.

Maintains accuracy with up to 40% malicious participants.

Abstract

Federated learning (FL) enables collaborative training of machine learning models without sharing training data. Traditional FL heavily relies on a trusted centralized server. Although decentralized FL eliminates the central dependence, it may worsen the other inherit problems faced by FL such as poisoning attacks and data representation leakage due to insufficient restrictions on the behavior of participants, and heavy communication cost, especially in fully decentralized scenarios, i.e., peer-to-peer (P2P) settings. In this paper, we propose a blockchain-based fully decentralized P2P framework for FL, called BlockDFL. It takes blockchain as the foundation, leveraging the proposed PBFT-based voting mechanism and two-layer scoring mechanism to coordinate FL among peer participants without mutual trust, while effectively defending against poisoning attacks. Gradient compression is introduced to lowering communication cost and prevent data from being reconstructed from transmitted model updates. Extensive experiments conducted on two real-world datasets exhibit that BlockDFL obtains competitive accuracy compared to centralized FL and can defend poisoning attacks while achieving efficiency and scalability. Especially when the proportion of malicious participants is as high as 40%, BlockDFL can still preserve the accuracy of FL, outperforming existing fully decentralized P2P FL frameworks based on blockchain.