Mitigating Privacy Risk via Forget Set-Free Unlearning
Organizations: University of Toronto, Vector Institute, Toronto, ON, Canada
Abstract
Training machine learning models requires the storage of large datasets, which often contain sensitive or private data. Storing data is associated with a number of potential risks which increase over time, such as database breaches and malicious adversaries. Machine unlearning is the study of methods to efficiently remove the influence of training data subsets from previously-trained models. Existing unlearning methods typically require direct access to the "forget set" -- the data to be forgotten-and organisations must retain this data for unlearning rather than deleting it immediately upon request, increasing risks associated with the forget set. We introduce partially-blind unlearning -- utilizing auxiliary information to unlearn without explicit access to the forget set. We also propose a practical framework Reload, a partially-blind method based on gradient optimization and structured weight sparsification to operationalize partially-blind unlearning. We show that Reload efficiently unlearns, approximating models retrained from scratch, and outperforms several forget set-dependent approaches. On language models, Reload unlearns entities using <0.025% of the retain set and <7% of model weights in <8 minutes on Llama2-7B. In the corrective case, Reload achieves unlearning even when only 10% of corrupted data is identified.
Figures & tables
| 10% Random | 100 In-Class | Entity Unlearning 1% | |||||
|---|---|---|---|---|---|---|---|
| Algorithm | FA ( ) | FMIA ( ) | FA ( ) | FMIA ( ) | Algorithm | FQ ( ) | MU ( ) |
| GA | GA | ||||||
| SSD | Grad Diff | ||||||
| SCRUB | NPO-RT | ||||||
| CF- | Pref Opt | ||||||
| SalUn | ECO (Zero-Out) | ||||||
Appendix figures & tables51 assets
Supplementary material from the paper’s appendix.
Appendix
| Statistic | Abbr. | Description |
|---|---|---|
| Accuracy on | RA | Model accuracy on the . In unlearning, a higher accuracy indicates that the unlearning process has not negatively impacted the model’s performance on the retained data. |
| Diff. in Accuracy on ( ) | FA | The change in accuracy on the forget set between the current model and . A smaller difference, approaching the accuracy of the retrained model, indicates that the unlearning method has been more effective in "forgetting" the forget set. |
| Diff. in Error on ( ) | FE | The reduction in error on the forget set between the current model and . A smaller difference, approaching the error of the retrained model, signifies that the unlearning method has been more effective at "forgetting" the forget set. |
| Diff. in MIA Success Rate on ( ) | FMIA | Difference in success rate of a membership inference attack (MIA) on the forget set between the current model and . In this work, we use the attack from ( Shokri et al., 2017 ) implemented in the repository for ( Kurmanji et al., 2023 ) . A success rate approaching that of the retrained model implies the forgotten data is indistinguishable to an MIA on in-distribution data that the model was not trained on. |
| Symmetric KL-Divergence on ( ) | RSKL | Symmetric KL-Divergence between the logits of the current model and those of . This metric is averaged over all instances in the . A lower symmetric KL divergence indicates an unlearning method that behaves similarly on the to a model retrained from scratch without the forget set. |
| Symmetric KL-Divergence on ( ) | FSKL | The Symmetric KL-Divergence between the logits of the current model and those of . This metric is averaged over all instances in the . A lower symmetric KL divergence indicates that the unlearning method that behaves similarly on the to a model retrained from scratch without the forget set. |
| Statistic | Abbr. | Description |
|---|---|---|
| Retain Accuracy | Acc | Model accuracy on a held out test set ( ) of the same distribution as . In corrective unlearning, a higher accuracy indicates that the corrective unlearning process has correctly adapted the model to its new training set. |
| Corrected Accuracy | Acc | Model accuracy on the adversely affected data . In the case of backdoor attacks or noisy corrective unlearning, a higher value indicates the relearned model correctly has lost its reliance on the backdoor pattern. In label correction setting, the desirable value is the percentage of samples that did not have their labels flipped (in our experiments, ). |
| Cost ( ) | Cost | Ratio of the runtime of the corrective unlearning method to the runtime of retraining a baseline model from scratch without the forget set. A lower cost indicates a more computationally efficient method. |
| Method | RA | FA | FE | FMIA | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|
| GA | |||||||
| FT | |||||||
| SSD | |||||||
| SCRUB | |||||||
| CF- | |||||||
| EU- |
| Method | RA | FA | FE | FMIA | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|
| GA | |||||||
| FT | |||||||
| SSD | |||||||
| SCRUB | |||||||
| CF- | |||||||
| EU- |
| Method | RA | FA | FE | FMIA | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|
| GA | |||||||
| FT | |||||||
| SSD | |||||||
| SCRUB | |||||||
| CF- | |||||||
| EU- |
| Method | RA | FA | FE | FMIA | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|
| GA | |||||||
| FT | |||||||
| SSD | |||||||
| SCRUB | |||||||
| CF- | |||||||
| EU- |
| Method | RA | FA | FE | FMIA | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|
| GA | |||||||
| FT | |||||||
| SSD | |||||||
| SCRUB | |||||||
| CF- | |||||||
| EU- |
| Method | RA | FA | FE | FMIA | AUC | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|---|
| GA | ||||||||
| FT | ||||||||
| SSD | ||||||||
| SCRUB | ||||||||
| CF-k | ||||||||
| EU-k |
| Method | RA | FA | FE | FMIA | AUC | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|---|
| GA | ||||||||
| FT | ||||||||
| SSD | ||||||||
| SCRUB | ||||||||
| CF-k | ||||||||
| EU-k |
| Method | RA | FA | FE | FMIA | AUC | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|---|
| GA | ||||||||
| FT | ||||||||
| SSD | ||||||||
| SCRUB | ||||||||
| CF-k | ||||||||
| EU-k |
| Method | RA | FA | FE | FMIA | AUC | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|---|
| GA | ||||||||
| FT | ||||||||
| SSD | ||||||||
| SCRUB | ||||||||
| CF-k | ||||||||
| EU-k |
| Method | RA | FA | FE | FMIA | AUC | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|---|
| GA | ||||||||
| FT | ||||||||
| SSD | ||||||||
| SCRUB | ||||||||
| CF-k | ||||||||
| EU-k |
| Method | RA | FA | FE | FMIA | AUC | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|---|
| GA | ||||||||
| FT | ||||||||
| SSD | ||||||||
| SCRUB | ||||||||
| CF-k | ||||||||
| EU-k |
| Method | RA | FA | FE | FMIA | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|
| GA | |||||||
| FT | |||||||
| SSD | |||||||
| SCRUB | |||||||
| CF- | |||||||
| EU- |
| Method | RA | FA | FE | FMIA | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|
| GA | |||||||
| FT | |||||||
| SSD | |||||||
| SCRUB | |||||||
| CF- | |||||||
| EU- |
| Method | RA | FA | FE | FMIA | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|
| GA | |||||||
| FT | |||||||
| SSD | |||||||
| SCRUB | |||||||
| CF- | |||||||
| EU- |
| Method | RA | FA | FE | FMIA | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|
| GA | |||||||
| FT | |||||||
| SSD | |||||||
| SCRUB | |||||||
| CF- | |||||||
| EU- |
| Method | RA | FA | FE | FMIA | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|
| GA | |||||||
| FT | |||||||
| SSD | |||||||
| SCRUB | |||||||
| CF- | |||||||
| EU- |
| Method | RA | FA | FE | FMIA | Cost | RSKL | FSKL |
|---|---|---|---|---|---|---|---|
| GA | |||||||
| FT | |||||||
| SSD | |||||||
| SCRUB | |||||||
| CF- | |||||||
| EU- |
| Split | Method | Change in Model Utility from Original | Forget Quality |
|---|---|---|---|
| 1% | Original | +0.0000 | 0.0030 |
| Retain | -0.0131 | 1.0000 | |
| Grad Ascent | -0.0233 | 0.0068 | |
| Grad Diff | -0.0198 | 0.0143 | |
| KL Min | -0.0221 | 0.0068 | |
| Pref Opt | -0.0021 | 0.0971 |
| Split | Method | Change in Model Utility from Original | Forget Quality |
|---|---|---|---|
| 10% | Original | 0.0000 | 0.0000 |
| Retain | +0.0053 | 1.0000 | |
| Grad Ascent | -0.5518 | 0.2107 | |
| Grad Diff | -0.1999 | 0.0000 | |
| KL Min | -0.5518 | 0.4158 | |
| Pref Opt | -0.0379 | 0.0000 |
| Cost ( ) | CIFAR10 | CIFAR100 |
|---|---|---|
| Poisoning | ||
| BadT | 0.44 | 0.68 |
| CF | 0.26 | 0.25 |
| SSD | 0.04 | 0.06 |
| Scrub | 0.26 | 0.31 |
| RewoD | 1.00 | 1.00 |
| Acc ( ) | CIFAR10 | CIFAR100 |
|---|---|---|
| Poisoning | ||
| None | 91.35 | 74.05 |
| BadT | 0.13 | 0.13 |
| CF | 0.09 | 0.54 |
| SSD | -3.05 | -2.08 |
| Scrub | 0.01 | 0.25 |
| Cost ( ) | CIFAR10 | CIFAR100 |
|---|---|---|
| Poisoning | ||
| BadT | 0.63 ±0.01 | 0.69 ±0.00 |
| CF | 0.26 ±0.01 | 0.25 ±0.00 |
| SSD | 0.06 ±0.01 | 0.06 ±0.00 |
| Scrub | 0.27 ±0.01 | 0.30 ±0.00 |
| RewoD | 1.00 ±0.04 | 1.00 ±0.01 |
| Acc ( ) | CIFAR10 | CIFAR100 |
|---|---|---|
| Poisoning | ||
| None | 91.35 | 74.05 |
| BadT | -0.02 ±0.06 | -0.13 ±0.15 |
| CF | 0.07 ±0.09 | 0.37 ±0.07 |
| SSD | -16.01 ±23.22 | 0.00 ±0.00 |
| Scrub | -0.01 ±0.01 | -0.01 ±0.06 |
| Experiment | Alpha ( ) | Ascent Learning Rate | Finetuning Learning Rate | Weight Reset Method |
|---|---|---|---|---|
| SVHN + ResNet-18 | 0.1 | 0.243 | 0.098 | Uniform |
| SVHN + VGG16-BN | 0.1 | 0.496 | 0.496 | Xavier Uniform |
| CIFAR-10 + ResNet-18 | 0.1 | 0.44 | 0.33 | Xavier Uniform |
| CIFAR-10 + VGG16-BN | 0.1 | 0.167 | 0.39 | Kaiming Uniform |
| CIFAR-100 + ResNet-18 | 0.1 | 0.18 | 0.33 | Xavier Normal |
| CIFAR-100 + VGG16-BN | 0.1 | 0.325 | 0.164 | Kaiming Normal |
| Experiment | Alpha ( ) | Ascent Learning Rate | Finetuning Learning Rate | Weight Reset Method | Retain Sample Size | Target Layers | Repair Epochs |
|---|---|---|---|---|---|---|---|
| Llama-2-7b-Chat + Forget01 | 0.008 | 0.039 | 0.0002 | Zero | 152 | mlp.gate_proj.weight | 5 |
| Llama-2-7b-Chat + Forget05 | 0.017 | 0.049 | 0.0002 | Uniform | 193 | self_attn.k_proj.weight | 5 |
| Llama-2-7b-Chat + Forget10 | 0.303 | 0.022 | 0.0488 | Xavier Uniform | 60 | self_attn.q_proj.weight | 28 |
| Phi-1.5 + Forget10 | 0.396 | 0.094 | 0.0445 | Uniform | 90 | self_attn.v_proj.weight | 40 |
| Experiment | Alpha ( ) | Ascent Learning Rate | Finetuning Learning Rate | Weight Reset Method |
|---|---|---|---|---|
| CIFAR10 + ResNet-9 + Poisoning | 0.3984 | 0.01 | 0.00381 | Xavier Normal |
| CIFAR10 + ResNet-9 + Interclass Confusion | 0.1978 | 0.01 | 0.00957 | Mean |
| CIFAR100 + ResNet-28x10 + Poisoning | 0.2401 | 0.01 | 0.00483 | Xavier Normal |
| CIFAR100 + ResNet-28x10 + Interclass Confusion | 0.0924 | 0.01 | 0.00237 | Zero |
| Acc retain ( ) | CIFAR10 | CIFAR100 |
|---|---|---|
| Poisoning | ||
| RELOAD | -2.84 ±2.56 | -5.08 ±1.39 |
| ReloadWithoutAscent | -3.28 ±2.49 | -5.24 ±1.65 |
| ReloadWithNormalisation | -4.23 ±2.11 | -5.34 ±1.72 |
| ReloadWithCosineKV | 0.24 ±0.12 | 0.49 ±0.15 |
| Interclass Confusion (IC) | ||
| Method | RA | FA | FE | FMIA | RSKL | FSKL |
|---|---|---|---|---|---|---|
| Reload (ours) | ||||||
| Retrained (Baseline) | - | - |
| Method | RA | FA | FE | FMIA | RSKL | FSKL |
|---|---|---|---|---|---|---|
| Reload (Un-Quantized) | ||||||
| Reload (Quantized) | ||||||
| Retrained (Baseline) | - | - |
| Method | RA | FA | FE | FMIA | RSKL | FSKL |
|---|---|---|---|---|---|---|
| Reload (ours) | ||||||
| Retrained (Baseline) | - | - |
| Method | RA | FA | FE | FMIA | RSKL | FSKL |
|---|---|---|---|---|---|---|
| Reload (ours) | ||||||
| Retrained (Baseline) | - | - |
| Method | RA | FA | FE | FMIA | RSKL | FSKL |
|---|---|---|---|---|---|---|
| Reload (ours) | ||||||
| Retrained (Baseline) | - | - |
| Method | RA | FA | FE | FMIA | RSKL | FSKL |
|---|---|---|---|---|---|---|
| Reload (10% of ) | ||||||
| Reload (20% of ) | ||||||
| Reload (30% of ) | ||||||
| Reload (40% of ) | ||||||
| Reload (50% of ) | ||||||
| Reload (60% of ) |
| Forgetting a Random 30% of the Data | Forgetting a Random Feature | ||||||||
| Method | RA | FA | FE | FMIA | Cost | OA | RA | TA | Cost |
| Original | N/A | N/A | N/A | N/A | N/A | N/A | |||
| Retrain | |||||||||
| Reload | |||||||||
| GA | |||||||||
| FT | |||||||||
Machine Unlearning
Machine unlearning removes the influence of selected data or concepts from trained models while preserving useful behavior and avoiding full retraining.
See all 343 papers