Research map / Adversarial robustness and security / Certified and empirical robustness
Universal Robustness via Median Randomized Smoothing for Real-World Super-Resolution
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Proposes CertSR, a real-world super-resolution model built on ESRGAN that combines median randomized smoothing fine-tuning and inference to achieve robustness to diverse adversarial attacks and real-world corruptions, compared against PGD/FGSM/BIM/CW adversarial training.
Problem
Real-world single-image super-resolution fails on unseen corruptions and sensor noise, and existing robust SR (adversarial training) methods are attack-specific and do not generalize across attack types.
Approach
Applies median randomized smoothing (percentile smoothing of a Gaussian-perturbed SR network, with certified L2 bounds) to SR, using pixel-wise median over only about 21 Gaussian samples and fine-tuning on Gaussian-noised LR images, rather than adversarial training with attack-specific perturbations.
Key results
- CertSR achieves LPIPS 0.19 on noisy DIV2K vs 0.67 for ESRGAN and 0.37 for AD-L-PGD, with PSNR 26.35.
- Under adversarial attacks, CertSR gets best PSNR/SSIM/LPIPS against most attacks, e.g. LPIPS 0.18 under CW vs 0.61 for AD-L-CW (PSNR 26.66).
- On real-world NTIRE and AIM validation sets, CertSR gets the best average LPIPS (0.27) without training on those datasets.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use median randomized smoothing fine-tuning and inference instead of adversarial training | ESRGAN for robust super-resolution · DIV2K validation, noisy | LPIPS: 0.29 -> 0.19 | Helped |
| Use median randomized smoothing fine-tuning and inference instead of adversarial training | ESRGAN for robust super-resolution · DIV2K validation, blurry | LPIPS: 0.48 -> 0.44 | Helped |
| Use median randomized smoothing fine-tuning and inference instead of FGSM adversarial training | ESRGAN for robust super-resolution · DIV2K validation, FGSM attack | LPIPS: 0.19 -> 0.27 | Hurt |
| Use median randomized smoothing fine-tuning and inference instead of BIM adversarial training | ESRGAN for robust super-resolution · DIV2K validation, BIM attack | LPIPS: 0.26 -> 0.25 | Helped |
| Use median randomized smoothing fine-tuning and inference instead of PGD adversarial training | ESRGAN for robust super-resolution · DIV2K validation, PGD attack | LPIPS: 0.24 -> 0.24 | No clear effect |
| Use median randomized smoothing fine-tuning and inference instead of PGD adversarial training | ESRGAN for robust super-resolution · DIV2K validation, CW attack | LPIPS: 0.24 -> 0.18 | Helped |
| Apply CertSR without training or fine-tuning on the evaluation dataset | ESRGAN for real-world super-resolution · NTIRE validation | LPIPS: 0.23 -> 0.21 | Helped |
| Apply CertSR without training or fine-tuning on the evaluation dataset | ESRGAN for real-world super-resolution · AIM validation | LPIPS: 0.36 -> 0.33 | Helped |
Surprising findings
- Adversarial-training model AD-L-CW performs worst on real-world LPIPS and on noisy data (PSNR 19.47), despite being the best RSR on clean data.
- Only about 21 Gaussian samples are needed for median smoothing in SR, versus around 2000 in classification and detection prior work.
Limitations
- Robustness is certified only for a chosen sigma per perturbation, so the sigma must be tuned per corruption type.
- Median smoothing on blurry inputs gives only marginal gains over ESRGAN (LPIPS 0.44 vs 0.48, PSNR 22.11 vs 22.23).
Experimental setup
Datasets: DIV2K Flickr2K NTIRE 2020 real-world SR validation AIM 2019 real-world SR validation
Benchmarks: DIV2K validation NTIRE 2020 real-world SR AIM 2019 real-world SR
Metrics: PSNR SSIM LPIPS
Baselines: ESRGAN AD-L-PGD AD-L-FGSM AD-L-BIM AD-L-CW Impressionism ESRGAN-FS
Builds on: ESRGAN Median randomized smoothing Robust Super-Resolution (Castillo et al.) PGD adversarial training
Closest papers by meaning
- The Perception-Robustness Tradeoff in Deterministic Image Restoration (ICML 2024 · similarity 0.87)
- Noise-Free Optimization in Early Training Steps for Image Super-resolution (AAAI 2024 · similarity 0.86)
- NSARM: Next-Scale Autoregressive Modeling for Robust Real-World Image Super-Resolution (NeurIPS 2026 · similarity 0.86)
- Augmenting Perceptual Super-Resolution via Image Quality Predictors (CVPR 2025 · similarity 0.86)
- Low-Res Leads the Way: Improving Generalization for Super-Resolution by Self-Supervised Learning (CVPR 2024 · similarity 0.85)
- Uncertainty-Aware GAN for Single Image Super Resolution (AAAI 2024 · similarity 0.85)
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