The Right to be Forgotten in Federated Learning: An Efficient Realization with Rapid Retraining
Open accessAbstract
In Machine Learning, the emergence of the right to be forgotten gave birth to a paradigm named machine unlearning, which enables data holders to proactively erase their data from a trained model. Existing machine unlearning techniques focus on centralized training, where access to all holders’ training data is a must for the server to conduct the unlearning process. It remains largely underexplored about how to achieve unlearning when full access to all training data becomes unavailable. One noteworthy example is Federated Learning (FL), where each participating data holder trains locally, without sharing their training data to the central server. In this paper, we investigate the problem of machine unlearning in FL systems. We start with a formal definition of the unlearning problem in FL and propose a rapid retraining approach to fully erase data samples from a trained FL model. The resulting design allows data holders to jointly conduct the unlearning process efficiently while keeping their training data locally. Our formal convergence and complexity analysis demonstrate that our design can preserve model utility with high efficiency. Extensive evaluations on four real-world datasets illustrate the effectiveness and performance of our proposed realization.
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The solution by Liu et al. [93] will result in a significant reduction in accuracy when dealing with complex models.
“However, this solution will result in a significant reduction in accuracy when dealing with complex models.”
From Machine Unlearning: A Survey (2024) · cites this paper as [93]
The Evaluation (p. 9) reports that Liu et al.’s algorithm achieves accuracy comparable to retraining from scratch and says momentum compensates for the model-utility loss from its approximation. The Introduction (p. 2) describes the solution as model agnostic and reports only a small accuracy loss on CelebA, contrary to the claimed significant reduction for complex models. (LLM, conf=0.87)
Checked by a reasoning model — may be wrong.
Experimental — accuracy not yet measuredThe second metric by Liu et al. [93] is the difference between the distribution of the model after the unlearning process and the distribution of the retraining model.
“The second metric is the difference between the distribution of the model after the unlearning process and the distribution of the retraining model.”
From Machine Unlearning: A Survey (2024) · cites this paper as [93]
The Experiment Setup (p. 8) explicitly identifies the second evaluation metric as Symmetric Absolute Percentage Error between the test accuracies of the unlearned model and the retraining baseline, not a difference between their model distributions. The paper separately discusses approximately identical model distributions as an unlearning criterion (Formalizing the Problem, p. 4), but does not define that as its second metric. (LLM, conf=0.87)
Checked by a reasoning model — may be wrong.
Experimental — accuracy not yet measuredLiu et al. [93] transferred the unlearning method from a centralized environment to federated learning by proposing a distributed Newton-type model updating algorithm to approximate the loss function trained by the local optimizer on the remaining dataset.
“Liu et al. [93] transferred the unlearning method from a centralized environment to federated learning by proposing a distributed Newton-type model updating algorithm to approximate the loss function trained by the local optimizer on the remaining dataset.”
From Machine Unlearning: A Survey (2024) · cites this paper as [93]
Liu et al. [93] use diagonal empirical Fisher Information Matrix (FIM) to efficiently and accurately approximate the inverse Hessian vector, rather than computing it directly, to further reduce the cost of the retraining process.
“They also use diagonal empirical Fisher Information Matrix (FIM) to efficiently and accurately approximate the inverse Hessian vector, rather than computing it directly, to further reduce the cost of the retraining process.”
From Machine Unlearning: A Survey (2024) · cites this paper as [93]
The method by Liu et al. [93] is based on the Quasi-Newton method and uses a first-order Taylor expansion.
“This method is based on the Quasi-Newton method and uses a first-order Taylor expansion.”
From Machine Unlearning: A Survey (2024) · cites this paper as [93]
The first metric by Liu et al. [93], Symmetric Absolute Percentage Error (SAPE), is created based on accuracy.
“The first metric, Symmetric Absolute Percentage Error (SAPE) , is created based on accuracy.”
From Machine Unlearning: A Survey (2024) · cites this paper as [93]
Liu et al. [93] analyzed the validity of the unlearning scheme through two aspects.
“Liu et al. [93] analyzed the validity of the unlearning scheme through two aspects.”
From Machine Unlearning: A Survey (2024) · cites this paper as [93]
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References 40 · Cited by 202
Research works printed but not linked: 17
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- Authors
- Liu, Y., Xu, L., Yuan, X., Wang, C., & Li, B.
- Affiliations
- City University of Hong Kong (HK)
- Nanjing University of Science and Technology (CN)
- Monash University (AU)
- Hong Kong University of Science and Technology (HK)
- Venue
- IEEE INFOCOM 2022 - IEEE Conference on Computer Communications
- Publisher
- IEEE
- Published
- 2022-05-02
- Pages
- 1749-1758
- OpenAlex
- W4221165231
- Cited by
- 202
- References
- 40
- Citations by year
- 2026: 38 · 2025: 74 · 2024: 62 · 2023: 25 · 2022: 3
- FWCI
- 22.65
- Type
- conference paper
- Language
- en
- Open access
- green
- arxiv.org
- Locations
- IEEE Conference on Computer Communications (INFOCOM) (publishedVersion)
- arXiv (Cornell University) (submittedVersion)
- Rare & Special e-Zone (The Hong Kong University of Science and Technology) (submittedVersion)
- arXiv (Cornell University)
- Funders
- National Natural Science Foundation of China
- Natural Science Foundation of Jiangsu Province
- Australian Research Council
- Topics
- Physical Sciences › Computer Science › Artificial Intelligence › Privacy-Preserving Technologies in Data
- Physical Sciences › Computer Science › Information Systems › Cloud Data Security Solutions
- Physical Sciences › Computer Science › Artificial Intelligence › Cryptography and Data Security
- Keywords
- right to be forgotten, machine unlearning, federated learning, model utility preservation, convergence analysis, computational complexity
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