FedRW: Efficient Privacy-Preserving Data Reweighting for Enhancing Federated Learning of Language Models

Pukang Ye (East China Normal University) · Luo Junwei · Jiachen Shen (East China Normal University) · Saipan Zhou (East China Normal University) · Shangmin Dou (ZStack) · Zhenfu Cao (East China Normal University) · Hanzhe Yao (East China Normal University) · Xiaolei Dong (East China Normal University) · Yunbo Yang (Zhejiang University)

adaptive reweighting mechanismdata duplicationfederated learningfrequency-aware reweightinggeneralizationglobal sample frequenciesparallel orchestration strategypreprocessing speedupprivacy-preserving frameworkrobustnesssample reweightingsecure multi-party computationsecurity guaranteessoft deduplication

Data duplication within large-scale corpora often impedes large language models' (LLMs) performance and privacy. In privacy-concerned federated learning scenarios, conventional deduplication methods typically rely on trusted third parties to perform uniform deletion, risking loss of informative samples while introducing privacy vulnerabilities. To address these gaps, we propose Federated ReWeighting (FedRW), the first privacy-preserving framework, to the best of our knowledge, that performs soft deduplication via sample reweighting instead of deletion in federated LLM training, without assuming a trusted third party. At its core, FedRW proposes a secure, frequency-aware reweighting protocol through secure multi-party computation, coupled with a parallel orchestration strategy to ensure efficiency and scalability. During training, FedRW utilizes an adaptive reweighting mechanism with global sample frequencies to adjust individual loss contributions, effectively improving generalization and robustness. Empirical results demonstrate that FedRW outperforms the state-of-the-art method by achieving up to $28.78\times$ speedup in preprocessing and approximately $11.42$\% improvement in perplexity, while offering enhanced security guarantees. FedRW thus establishes a new paradigm for managing duplication in federated LLM training.