Certified Robustness under Heterogeneous Perturbations via Hybrid Randomized Smoothing

Fuente: arXiv
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Main Authors: Delattre, Blaise, Wu, Hengyu, Caillon, Paul, Lim, Wei Yang Bryan, Cao, Yang
Format: Preprint
Published: 2026
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author Delattre, Blaise
Wu, Hengyu
Caillon, Paul
Lim, Wei Yang Bryan
Cao, Yang
author_facet Delattre, Blaise
Wu, Hengyu
Caillon, Paul
Lim, Wei Yang Bryan
Cao, Yang
contents Randomized smoothing provides strong, model-agnostic robustness certificates, but existing guarantees are limited to single modalities, treating continuous and discrete inputs in isolation. This limitation becomes critical in multimodal models, where decisions depend on cross-modal semantics and adversaries can jointly perturb heterogeneous inputs, rendering unimodal certificates insufficient. We introduce a unified randomized smoothing framework for mixed discrete--continuous inputs based on an analytically tractable Neyman--Pearson formulation of the joint worst-case problem. By analyzing the joint likelihood ordering induced by factorized discrete and continuous noise, our approach yields a closed-form, one-dimensional certificate that strictly generalizes both Gaussian (image-only) and discrete (text-only) randomized smoothing. We validate the framework on multimodal safety filtering, providing, to our knowledge, the first model-agnostic Neyman--Pearson certificate for joint discrete-token and continuous-image perturbations in interaction-dependent text--image safety filtering.
format Preprint
id arxiv_https___arxiv_org_abs_2605_12876
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Certified Robustness under Heterogeneous Perturbations via Hybrid Randomized Smoothing
Delattre, Blaise
Wu, Hengyu
Caillon, Paul
Lim, Wei Yang Bryan
Cao, Yang
Machine Learning
Randomized smoothing provides strong, model-agnostic robustness certificates, but existing guarantees are limited to single modalities, treating continuous and discrete inputs in isolation. This limitation becomes critical in multimodal models, where decisions depend on cross-modal semantics and adversaries can jointly perturb heterogeneous inputs, rendering unimodal certificates insufficient. We introduce a unified randomized smoothing framework for mixed discrete--continuous inputs based on an analytically tractable Neyman--Pearson formulation of the joint worst-case problem. By analyzing the joint likelihood ordering induced by factorized discrete and continuous noise, our approach yields a closed-form, one-dimensional certificate that strictly generalizes both Gaussian (image-only) and discrete (text-only) randomized smoothing. We validate the framework on multimodal safety filtering, providing, to our knowledge, the first model-agnostic Neyman--Pearson certificate for joint discrete-token and continuous-image perturbations in interaction-dependent text--image safety filtering.
title Certified Robustness under Heterogeneous Perturbations via Hybrid Randomized Smoothing
topic Machine Learning
url https://arxiv.org/abs/2605.12876