Hollow-LLM Attack: Ghost Weights That Fool Zero-Knowledge LLM Verification

A new paper on arXiv (submitted 30 Jul 2026) introduces the Hollow-LLM Attack, showing that zero-knowledge (ZK) verification of large language model (LLM) inference can be fooled by dishonest providers who embed 'ghost weights' that collapse effective computation while still satisfying the verification circuit. The attack allows providers to deliver provably correct outputs at small-model cost while overclaiming model size, with zero quality loss under the same verification circuit, highlighting that proof of correct inference is not proof of large-model execution.

Computer Science Cryptography and Security Submitted on 30 Jul 2026 Title:Hollow-LLM Attack: Computationally Trivial Weights in Zero-Knowledge Verification of LLM Inference View PDF /pdf/2607.28884 HTML experimental https://arxiv.org/html/2607.28884v1 Abstract:As large language models LLMs grow in scale and are predominantly served from remote platforms, verifying faithful inference execution becomes critical i.e., ensuring that a provider actually executes the advertised model and computational workload rather than a tampered or downsized variant . Zero-knowledge ZK LLM inference offers an appealing approach. It promises public verifiability and delivers per-instance guarantees of equational correctness by proving that an output is consistent with executing a public architecture under committed, private weights. Though, we show that it does not bind the effort expended to produce the output. In this paper, we formalize this overlooked effort gap and introduce the Hollow-LLM Attack, in which a dishonest provider retains the declared architecture and parameter count but embeds ghost weights whose algebraic structure collapses effective computation. These witnesses satisfy the verification circuit and yield valid proofs, even though the dishonest model owner, who serves as the prover, performs computation commensurate with a much smaller model than the declared public architecture. This creates a profitable equilibrium in which providers deliver provably correct outputs at small-model cost while overclaiming model size. Accordingly, we characterize concrete families of ghost weights that compose with standard transformer blocks and show that such hollow deployments substantially reduce serving cost with zero quality loss under the same verification circuit. These findings underscore that proof of correct inference is not proof of large-model execution and necessitate additional protections to bind correctness to verifiable computational work. References & Citations Loading... Bibliographic and Citation Tools Bibliographic Explorer What is the Explorer? https://info.arxiv.org/labs/showcase.html arxiv-bibliographic-explorer Connected Papers What is Connected Papers? https://www.connectedpapers.com/about Litmaps What is Litmaps? https://www.litmaps.co/ scite Smart Citations What are Smart Citations? https://www.scite.ai/ Code, Data and Media Associated with this Article alphaXiv What is alphaXiv? https://alphaxiv.org/ CatalyzeX Code Finder for Papers What is CatalyzeX? https://www.catalyzex.com DagsHub What is DagsHub? https://dagshub.com/ Gotit.pub What is GotitPub? http://gotit.pub/faq Hugging Face What is Huggingface? https://huggingface.co/huggingface ScienceCast What is ScienceCast? https://sciencecast.org/welcome Demos Recommenders and Search Tools Influence Flower What are Influence Flowers? https://influencemap.cmlab.dev/ CORE Recommender What is CORE? https://core.ac.uk/services/recommender arXivLabs: experimental projects with community collaborators arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website. Both individuals and organizations that work with arXivLabs have embraced and accepted our values of openness, community, excellence, and user data privacy. arXiv is committed to these values and only works with partners that adhere to them. Have an idea for a project that will add value for arXiv's community? Learn more about arXivLabs https://info.arxiv.org/labs/index.html .