Harnessing the benefits of blockchain, such as decentralization, immutability, and transparency, to bolster the credibility and security attributes of federated learning (FL) has garnered increasing attention. However, blockchain-enabled FL (BFL) still faces several challenges. The primary and most significant issue arises from its essential but slow validation procedure, which selects high-quality local models by recruiting distributed validators. The second issue stems from its incentive mechanism under the transparent nature of blockchain, increasing the risk of privacy breaches regarding workers’ cost information. The final challenge involves data eavesdropping from shared local models. To address these significant obstacles, this paper proposes a Blockchain-enabled Incentivized and Secure Federated Learning (BIT-FL) framework. BIT-FL leverages a novel loop-based sharded consensus algorithm to accelerate the validation procedure, ensuring the same security as non-sharded consensus protocols. It consistently outputs the correct local model selection when the fraction of adversaries among validators is less than$1/2$with synchronous communication. Furthermore, BIT-FL integrates a randomized incentive procedure, attracting more participants while guaranteeing the privacy of their cost information through meticulous worker selection probability design. Finally, by adding artificial Gaussian noise to local models, it ensures the privacy of trainers’ local models. With the careful design of Gaussian noise, the excess empirical risk of BIT-FL is upper-bounded by$\mathcal {O}(\frac{\ln n_{\min}}{ n_{\min}^{3/2}}+\frac{\ln n}{n})$, where$n$represents the size of the union dataset, and$n_{{\min}}$represents the size of the smallest dataset. Our extensive experiments demonstrate that BIT-FL exhibits efficiency, robustness, and high accuracy for both classification and regression tasks.

Due to the progress in computer hardware and network technologies, federated learning (FL), a decentralized training method in machine learning, has garnered widespread attention. In this approach, individuals share local model parameters rather than raw training data to protect their privacy. However, the inherent heterogeneity of practical computing devices poses challenges to the efficiency and performance of FL. In this paper, we explore the landscape of heterogeneous FL frameworks and introduce ChronusFed, a reinforCement-based adaptive partial training method for heterogeneous Federated learning. ChronusFed employs a dynamic epoch adjustment mechanism (DEA) and a customizable partial training framework (CPT) to optimize model training efficiency. By integrating DEA and CPT, ChronusFed effectively tackles the straggler issues that arise from limited hardware resources, while simultaneously enhancing the model performance. More specifically, DEA leverages deep reinforcement learning (DRL) to model the current state of the global model and determine optimal local training epochs, while CPT utilizes our proposed maximum coverage algorithm to handle device heterogeneity and accelerate model convergence. Theoretical analysis of training convergence validates the effectiveness of ChronusFed, and comprehensive experimental evaluations demonstrate that ChronusFed outperforms state-of-the-art methods across various learning tasks, showcasing its robustness and superiority in heterogeneous FL scenarios.