Research map / Adversarial robustness and security / Certified and empirical robustness
Optimizing Robustness and Accuracy in Mixture of Experts: A Dual-Model Approach
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Shows that MoE experts are more adversarially vulnerable than the router, proposes RT-ER (KL-regularized robust training of the second-top expert), a dual-model linear combination of standard and robust MoE with certified bounds, and a bi-level joint training (JTDMoE) that improves SA and RA on CIFAR-10 and TinyImageNet.
Problem
Adversarial robustness of Mixture of Experts models is poor, and existing robust training methods for MoE either ignore component-level vulnerability or sacrifice substantial standard accuracy.
Approach
Identify experts (not the router) as the vulnerable MoE component, robustify only the second-top expert via an added KL term, and combine a standard and a robust MoE with a smoothing parameter alpha, jointly trained with a bi-level scheme to recover clean accuracy while keeping certified robustness bounds.
Key results
- On CIFAR-10 (ResNet18 experts), RT-ER reaches 69.09% PGD robust accuracy vs 53.74% for AT, at 77.81% SA.
- JTDMoE on CIFAR-10 at alpha=0.7 achieves 92.29% SA and 74.62% PGD RA, versus 89.81% SA and 67.81% RA for the pre-trained dual-model.
- Under AutoAttack on CIFAR-10, JTDMoE improves RA from 33.64% to 54.55% over the pre-trained dual-model.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Add KL-based robustification of the second-top expert | ResNet18 MoE · CIFAR-10, PGD | RA: 53.74 -> 69.09 | Helped |
| Add KL-based robustification of the second-top expert | ViT-small MoE · TinyImageNet, PGD | RA: 50.94 -> 56.79 | Helped |
| Add KL-based robustification of the second-top expert | ResNet18 MoE · CIFAR-10, PGD | SA: 79.08 -> 77.81 | Hurt |
| Jointly train the standard and robust MoE | Pre-trained dual-model, α=0.7 · CIFAR-10, PGD | RA: 67.81 -> 74.62 | Helped |
| Jointly train the standard and robust MoE | Pre-trained dual-model, α=0.7 · TinyImageNet, PGD | RA: 53.11 -> 57.39 | Helped |
| Jointly train the standard and robust MoE | Pre-trained dual-model, α=0.7 · CIFAR-10, AutoAttack | RA: 33.64 -> 54.55 | Helped |
| Increase α from 0.7 to 0.9 (ablation) | Pre-trained dual-model · CIFAR-10, PGD | SA: 89.81 -> 83.27 | Hurt |
| Increase α from 0.7 to 0.9 (ablation) | Pre-trained dual-model · CIFAR-10, PGD | RA: 67.81 -> 70.73 | Helped |
| Increase the number of experts from 3 to 5 (ablation) | RT-ER · CIFAR-10, PGD | RA: 69.03 -> 70.00 | Helped |
| Increase KL-loss weight β from 1 to 6 (ablation) | RT-ER · CIFAR-10, PGD | RA: 64.13 -> 69.09 | Helped |
| Increase KL-loss weight β from 6 to 9 (ablation) | RT-ER · CIFAR-10, PGD | RA: 69.09 -> 10 | Hurt |
| Use a smooth dense approximation for expert selection during attack | RT-ER · CIFAR-10, smooth attack | RA: 51.03 -> 68.96 | Helped |
Surprising findings
- Experts are far more vulnerable than the router: RA-E drops below 4% on CIFAR-10 under PGD while RA-R stays above 50%.
- Setting the KL weight beta=9 collapses all metrics to 10% (random guessing) when training from scratch.
Limitations
- Theoretical bounds rely on an assumption of Lipschitz continuity of experts and router that holds only under stated scenarios.
- Large SA loss for single-model robust training (e.g., RT-ER SA 77.81% vs ST 92.14%) motivates the dual-model, which is only partly recovered.
- Dual-model is built by combining pretrained models for efficiency rather than training from scratch; experiments limited to CIFAR-10 and TinyImageNet at small scale.
Experimental setup
Datasets: CIFAR-10 TinyImageNet ImageNet
Benchmarks: CIFAR-10 TinyImageNet ImageNet
Metrics: standard accuracy robust accuracy RA-E RA-R certified robustness bound
Baselines: Standard training (ST) Adversarial training (AT) TRADES AdvMoE Pre-trained Dual-Model
Builds on: PGD adversarial training TRADES AdvMoE Lipschitz-based certified robustness
Closest papers by meaning
- On Least Square Estimation in Softmax Gating Mixture of Experts (ICML 2024 · similarity 0.88)
- $\texttt{MoE-RBench}$: Towards Building Reliable Language Models with Sparse Mixture-of-Experts (ICML 2024 · similarity 0.88)
- On the Expressive Power of Mixture-of-Experts for Structured Complex Tasks (NeurIPS 2025 · similarity 0.88)
- Joint MoE Scaling Laws: Mixture of Experts Can Be Memory Efficient (ICML 2025 · similarity 0.88)
- A Provably Effective Method for Pruning Experts in Fine-tuned Sparse Mixture-of-Experts (ICML 2024 · similarity 0.88)
- MoDE: A Mixture-of-Experts Model with Mutual Distillation among the Experts (AAAI 2024 · similarity 0.88)
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