Characterizing the Training Dynamics of Private Fine-tuning with Langevin diffusion
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Abstract (arXiv)
We show that differentially private full fine-tuning (DP-FFT) can distort pre-trained backbone features based on both theoretical and empirical results. We identify the cause of the distortion as the misalignment between the pre-trained backbone and the randomly initialized linear head. We prove that a sequential fine-tuning strategy can mitigate the feature distortion: first-linear-probing-then-fine-tuning (DP-LP-FFT). A new approximation scheme allows us to derive approximate upper and lower bounds on the training loss of DP-LP and DP-FFT, in a simple but canonical setting of 2-layer neural networks with ReLU activation. Experiments on real-world datasets and architectures are consistent with our theoretical insights. We also derive new upper bounds for 2-layer linear networks without the approximation. Moreover, our theory suggests a trade-off of privacy budget allocation in multi-phase fine-tuning methods like DP-LP-FFT.
Key facts. Cited by 4 papers in the map (data through 14 Oct 2026). Builds on 37 of its 61 references that are in the map. First posted on arXiv 29 Feb 2024.
Builds on
37 of 61 references.
References · 37
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25 more
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Citing papers per year: 2024: 2; 2025: 2.
4 papers.
- 2024DP-MemArc: Differential Privacy Transfer Learning for Memory Efficient Language Modelscited by 2
- 2025On Optimal Hyperparameters for Differentially Private Deep Transfer Learningcited by 1
- 2024Mitigating Noise Detriment in Differentially Private Federated Learning with Model Pre-trainingcited by 0
- 2025Lower Bounds for Public-Private Learning under Distribution Shiftcited by 0
- 2025On Optimal Hyperparameters for Differentially Private Deep Transfer Learning23 Oct 2025
- 2025Lower Bounds for Public-Private Learning under Distribution Shift23 Jul 2025
- 2024Mitigating Noise Detriment in Differentially Private Federated Learning with Model Pre-training18 Aug 2024
- 2024DP-MemArc: Differential Privacy Transfer Learning for Memory Efficient Language Models16 Jun 2024