GOLIATH: Gradient Inversion of Tabular Diffusion Models

Gradient inversion reconstructs training data from shared gradients. However, existing methods target classification tasks and image diffusion, and do not address mixed tabular diffusion, where numerical columns follow Gaussian noising while categorical columns are corrupted by discrete masks. This mixed continuous-discrete training objective changes both the inversion target and the gradient structure: an attacker must recover not only rows, timesteps, and noise, but also the latent mask pattern whose density is tied to the diffusion timestep. We propose Goliath, the first gradient inversion attack designed for tabular diffusion models. Goliath employs a cyclic inversion loop that jointly recovers rows and diffusion latents across Gaussian and mixed diffusion regimes. We introduce a tabular-aware objective function that balances numerical and categorical gradient contributions while improving categorical recovery through enforced consistency between noise levels and mask structures. To accommodate large batches, we aggregate multiple reconstructions across epochs using a row-alignment heuristic. Evaluated across nine tabular datasets, Goliath achieves up to $88.9\\%$ per-cell reconstruction accuracy and consistently outperforms gradient-inversion baselines across Gaussian and mixed tabular diffusion. Code is available at https://anonymous.4open.science/r/fl-tab-diffusion-inversion-F4E7/README.md.