Swapping random decoders for diffusion language models in black-box attacks cut prompt perplexity from 10^3-10^7 down to 3-5
AspireAI community · arXiv
Continuous-space black-box attacks normally decode an optimized latent through a random mapping, which produces unnatural text that input guardrails can spot and makes the resulting risk estimates unrepresentative of real prompts. This paper couples the same latent-space search directly to a learned diffusion language model instead, removing the random mapping while keeping the Gaussian latent formulation and the sampling or optimization procedure intact. Applied to RareTrap (sampling) and ThinkTrap (optimization), character-level perplexity fell from 10^3 to 10^7 down to 3-5 and from 20-28 down to 4.3-5.4 respectively, and the authors report that measured model risk can differ by an order of magnitude between the two mappings. The practical implication for defenders is that attack cost and risk numbers depend heavily on how prompts are generated, so a red-team benchmark built on unnatural prompts may not describe real exposure. Caveat: the study targets overthinking-style behaviours under bounded generation budgets, not code execution or tool abuse, and no code release is linked from the paper.
Read the story and explore more from the AspireAI community.
Two sparse-autoencoder analyses have resisted scaling: matching semantically similar features across layers, and compressing large feature circuits into interpretable supernodes. This paper argues both are the same underlying problem, estimating semantic distances between SAE features that sit on different activation manifolds. Its representation treats each feature not as a single decoder vector but as an activation-weighted distribution over the hidden states expressing it, projects those distributions into a shared reference space, and compares them with Wasserstein distance. The representation is proved invariant to activation rescaling and stable under perturbation, and recovers true matches under finite-sample margin conditions. Empirically it outperformed decoder-vector and LLM-based baselines and captured subtle functional distinctions between related features, and it compressed large feature circuits into interpretable supernodes automatically. The limitation is that this is interpretability tooling: the paper demonstrates better feature matching and circuit compression, not that downstream interpretability claims become more accurate.