🤖 AI Summary
This work investigates how to quantify the minimal weight perturbation required to induce a specified output change in deep neural networks, with applications to analyzing and defending against backdoor attacks that exploit low-rank compressed activations. We derive, for the first time, closed-form expressions for the minimum-norm weight perturbations in both single-layer and multi-layer networks, revealing how backpropagation margins govern layer-wise sensitivity and establishing connections to Lipschitz-based robustness bounds. Building on these insights, we propose provable compression thresholds that delineate the feasibility boundary of backdoor attacks. Theoretical analysis and experiments demonstrate that low-rank compression can reliably trigger latent backdoors while preserving model accuracy, and simultaneously provide certifiable guarantees on the minimality of parameter updates needed for such attacks.
📝 Abstract
The minimal norm weight perturbations of DNNs required to achieve a specified change in output are derived and the factors determining its size are discussed. These single-layer exact formulae are contrasted with more generic multi-layer Lipschitz constant based robustness guarantees; both are observed to be of the same order which indicates similar efficacy in their guarantees. These results are applied to precision-modification-activated backdoor attacks, establishing provable compression thresholds below which such attacks cannot succeed, and show empirically that low-rank compression can reliably activate latent backdoors while preserving full-precision accuracy. These expressions reveal how back-propagated margins govern layer-wise sensitivity and provide certifiable guarantees on the smallest parameter updates consistent with a desired output shift.