基于动态可搜索混合加密技术的可信联邦学习方法

Trusted Federated Learning Method Based on Dynamic Searchable Hybrid Encryption Technology

  • 摘要: 针对现有密码学联邦学习方案在系统实体置信度低、加密计算效率瓶颈、中心化存储单点故障风险以及恶意节点投毒导致鲁棒性不足等关键问题,本文提出一种基于动态可搜索混合加密技术的可信联邦学习方案。本方案聚焦于解决分布式环境下的外部不可信实体威胁与隐私高预算冲突,通过引入动态可搜索加密与混合密码体制,在兼顾系统整体鲁棒性与运行性能的前提下,构建具备高系统实体置信度的去中心化可信联邦学习体系。首先,提出了一种轻量级双向身份验证与分布式密钥协商协议,支持第三方密钥管理实体与客户端在低交互开销下完成协商密钥计算,并引入混合加密机制实现对数据的差异化隐私保护与分布式密钥管理。其次,结合贡献度感知的本地评估与混合加密机制的安全聚合算法,实现公平、安全的密文参数聚合。最后,通过安全令牌驱动的访问控制与动态密钥轮换机制,构建中心化密文存储的可搜索关联性陷门索引,实现其不可重放性与历史数据不可揭示性。实验结果表明,本文所提方案与现有方案相比,MNIST数据集与Fashion-MNIST数据集中全局模型准确率分别能达到99.51%与93.91%,且对隐私数据的平均加密时间开销仅为0.24 s与0.42 s。另外,在客户端掉线率40%或数据缺失50%的极端条件下,全局模型准确率在MNIST和Fashion-MNIST数据集中仍能分别稳定在98%与90%以上。

     

    Abstract: Aimed at the key problems of existing cryptographic federated learning schemes, including low system entity trustworthiness, encryption efficiency bottlenecks, single-point-of-failure risks of centralized storage, and insufficient robustness resulting from malicious node poisoning, we present a trusted federated learning scheme based on dynamic searchable hybrid encryption. This scheme focuses on mitigating external untrusted entity threats and high privacy budget conflicts within distributed environments. By incorporating dynamic searchable encryption and hybrid cryptographic mechanisms, it constructs a decentralized, trusted federated learning system featuring high entity trustworthiness, while simultaneously balancing overall system robustness and operational performance. Firstly, we introduce a lightweight bidirectional authentication and distributed key negotiation protocol that enables third-party key management entities and clients to compute negotiated keys with low interaction overhead. This is complemented by a hybrid encryption mechanism to achieve differentiated privacy protection and distributed key management for data. Secondly, by integrating contribution-aware local evaluation with a secure aggregation algorithm based on hybrid encryption, we realize fair and secure ciphertext parameter aggregation. Finally, through security token-driven access control and dynamic key rotation mechanisms, we construct searchable associative trapdoor indexes for centralized ciphertext storage, ensuring non-replayability and non-revealability of historical data. Experimental results show that compared with the existing schemes, the global model accuracy of the MNIST dataset and Fashion-MNIST dataset can reach 99.51% and 93.91% respectively, and the average encryption time overhead of the proposed scheme for private data is only 0.24 s and 0.42 s. In addition, under the extreme conditions of 40% client drop rate or 50% data missing, the global model accuracy can still be stable, exceeding 98% on the MNIST dataset and 90% on the Fashion-MNIST dataset.

     

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