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Zero-knowledge proofs of inference and Timed challenge-response and memory-occupation challenges

No new hardware needed

Zero-knowledge proofs of inference and Timed challenge-response and memory-occupation challenges

Published attempts to break a system, including those that found failures. Testing history does not show that open flaws are resolved.

• Zero-knowledge proofs of inference: Independent red-team
• Timed challenge-response and memory-occupation challenges, VRAM-residency challenge: Analysis

Family findings

• Timed challenge-response and memory-occupation challenges

  Context for VRAM-residency challenge. These findings concern the family or other implementations; applicability must be checked against their stated scope.

  • Timing-based software attestation has been broken in practice in Timed challenge-response and memory-occupation challenges

    Castelluccia et al. implemented two generic attacks, one based on a return-oriented rootkit and one on code compression, together with specific attacks on SWATT and ICE-based schemes, on commodity sensor nodes. They conclude that secure time-based attestation is "very difficult, if not impossible, to design correctly". The attacks target embedded schemes, not AI accelerators. ^{14 15}

    Response: Perrig and van Doorn, two of the designers of SWATT and ICE, replied in August 2010. They argue that the rootkit attack defeats a naive implementation, not a property the schemes claim, and that the SWATT attack was run on a re-implementation on a chip with eight times the program memory, where SWATT's own chip is almost always full of code. They accept that the attack on ICE works.

    Demonstrated attack · Significant · Disputed. On the record

  • Remote memory narrows the timing margin in Timed challenge-response and memory-occupation challenges

    Data-centre remote memory access returns in about 1–2 µs, against about 70–200 ns for local DRAM. The MIRI overview says verification of memory saturation depends on ruling out remote access by latency or physical disconnection. It adds that pre-staging data is ruled out only by unpredictable, capacity-filling challenges. ¹¹

    Theoretical argument · Significant · Open. On the record

    Related mechanism R2 Bandwidth limits and compartmentalization: Physical disconnection is proposed to exclude remote memory between the separated groups during a challenge. It depends on the isolation boundary being enforced. A pointer, not evidence that this flaw is mitigated. Add

  • Error rates not quantified in Timed challenge-response and memory-occupation challenges

    Monfared et al. show separable timing distributions but do not define thresholds or statistical tests, so false-positive and false-negative rates are not quantified. ¹³

    Open question · Minor · Open. On the record

Open significant flaws

4 flaws in 2 mechanisms

• The proof covers a fixed-point approximation, not the floating-point model in Zero-knowledge proofs of inference

  Current ZK inference systems prove a quantised version of the network. zkLLM scales values by 2^16 and reports small perplexity changes. Attestable reports quantising matrix multiplications to 8-bit integers while proving other operations in floating point. A verifier therefore learns about the proof-friendly variant, and must separately accept that this variant is the declared model. Trail of Bits built a ResNet-18 backdoor that is dormant in the full-precision model and active after ezkl's quantisation; whether it persists through proving was left for further investigation. A verification system design calls floating-point emulation in ZKPs an open problem. ^{1 5 7 11}

  Open question · Significant · Open. On the record

• A proof speaks only for the computations that were proven in Zero-knowledge proofs of inference

  Attestable writes that "a proof of some computation is not a proof of all computation", and that a proof cannot discover a datacenter that was never declared. Proofs of inference do not by themselves show that no other workload ran on the same or other hardware. ¹²

  Theoretical argument · Significant · Open. On the record

  Related mechanism R1 Proofs of useful work for capacity accounting: The record names proof-of-work accounting as the kind of compute accounting needed to show that proven inference was the only work done. A pointer, not evidence that this flaw is mitigated. Add

• Proofs do not bind computational effort (Hollow-LLM) in Zero-knowledge proofs of inference

  Researchers at the University of Southern California show that a proof of inference certifies that an output is consistent with committed weights under the declared architecture, but not how much computation produced it. In their Hollow-LLM attack, a provider keeps the declared architecture and parameter count but commits to "ghost weights". Some layers pass their inputs through unchanged, and wide layers carry the signal in a small subspace, so a much smaller inner model does the real work. The ghost weights satisfy the verification circuit and yield valid proofs.

  The authors ran the attack with the proof procedure of zkGPT, a separate ZK inference system, on a 6-layer, 512-dimensional transformer declared as up to 12 layers and 1,024 dimensions. Outputs were identical to the inner model's, and serving cost stayed at the inner model's level. An honest model of the declared size cost 2.4 times as much to prefill and 3.1 times as much to decode. Proving cost still grew with the declared architecture.

  The authors note that results may be served before any proof, with the provider building the witness only when a call is selected for audit. They describe their constructions as "compatible with state-of-the-art zkLLM pipelines", and state that the attack does not imply a flaw in the proof system itself. They propose challenge-based audits and ablation tests, which raise the cost of cheating but give no guarantee. ¹⁰

  Demonstrated attack · Significant · Open. On the record

• Answers are not tied to one GPU in VRAM-residency challenge

  The paper's floating-point fingerprint characterises a GPU model. The authors state that it does not distinguish individual GPUs, so a timely answer does not show which device of that model held the data. ¹³

  Theoretical argument · Significant · Open. On the record

Open minor flaws

2 mechanisms with minor findings

• The model architecture is disclosed in Zero-knowledge proofs of inference

  ZKML "requires that the model architecture (but not weights) is revealed", and zkLLM assumes a publicly known model structure. Architecture can be commercially sensitive. ^{1 3}

  Theoretical argument · Minor · Open. On the record

• Error rates not quantified in VRAM-residency challenge

  Monfared et al. report a timing gap of more than 350 ms but leave hardware-specific thresholds to future work and state that false-positive and false-negative rates are not quantified. ¹³

  Open question · Minor · Open. On the record

Mechanisms on the map that are not in the proposal. Pointers, not recommendations. ?

• R1 Proofs of useful work for capacity accounting Add
  • Bears on the open significant flaw “A proof speaks only for the computations that were proven” in Zero-knowledge proofs of inference. The record names proof-of-work accounting as the kind of compute accounting needed to show that proven inference was the only work done.
  • Zero-knowledge proofs of inference waits on it. Showing that proven inference was the only work done needs a compute-accounting mechanism such as proof-of-work accounting, which is only proposed.

Blockers

6 blockers recorded

• Zero-knowledge proofs of inference
  • Proving takes about 13 minutes (803 seconds) per 2,048-token forward pass of a 13B model on one A100, and a verification system design calls the overhead heavy. Performance & compatibility ^{1 11}
  • ZKML and zkLLM prove fixed-point arithmetic, and floating-point emulation in ZKPs is described as an open problem. Performance & compatibility ^{1 3 11}
  • zkLLM's code is unaudited, interactive and archived; the one audited ZK inference library, ezkl, had high-severity circuit soundness bugs before its fixes. Adversarial validation ^{2 7}
  • Showing that proven inference was the only work done needs a compute-accounting mechanism such as proof-of-work accounting, which is only proposed. Coverage & hidden compute. Waits on Proofs of useful work for capacity accounting ¹²
• Timed challenge-response and memory-occupation challenges
  • The challenge data occupies a large part of GPU memory for as long as the test runs. Performance & compatibility ¹³
  • No test across servers has been reported, and the MIRI overview lists network-level probing of memory contents as undemonstrated. Adversarial validation ^{11 13}

From the family or selected implementation's record. ?

Model weights

Hidden by Zero-knowledge proofs of inference.

Unspecified for Timed challenge-response and memory-occupation challenges. Check the implementation record.

Inputs and outputs

Shown by Zero-knowledge proofs of inference.

Unspecified for Timed challenge-response and memory-occupation challenges. Check the implementation record.

Training data

Not involved: Zero-knowledge proofs of inference.

Unspecified for Timed challenge-response and memory-occupation challenges. Check the implementation record.

Zero-knowledge proofs of inference

• R1 Attestable zero-knowledge inference prover Product, Attestable
• R2 EZKL Product, Zkonduit
• R1 Low-trust AI compute verification system overview Proposed architecture, Machine Intelligence Research Institute
• R2 zkLLM Research prototype, University of Waterloo

Timed challenge-response and memory-occupation challenges

• R1 Data-centre memory challenging Proposed architecture, Machine Intelligence Research Institute
• R2 GPU contention probes Research prototype
• R1 Low-trust AI compute verification system overview Proposed architecture, Machine Intelligence Research Institute
• R2 SAGE Research prototype
• R2 VRAM-residency challenge Research prototype

1. zkLLM: Zero Knowledge Proofs for Large Language Models, H. Sun et al. (2024). Original
2. zkllm-ccs2024: code for zkLLM: Zero Knowledge Proofs for Large Language Models, H. Sun (2024). Original
3. ZKML: An Optimizing System for ML Inference in Zero-Knowledge Proofs, B.-J. Chen et al. (2024). Original
4. NanoZK: Privacy-Preserving Verifiable Inference for Large Language Models via Layerwise Zero-Knowledge Proofs, Z. Wang (2026). Original
5. Proving LLMs at Scale, Attestable (2026). Original
6. Verifiable evaluations of machine learning models using zkSNARKs, T. South et al. (2024). Original
7. Zkonduit EZKL Security Assessment, F. Casal et al. (2025). Original
8. DeepProve-1: The First zkML System to Prove a Full LLM Inference, Lagrange Labs (2025). Original
9. Lagrange-Labs/deep-prove (GitHub repository), Lagrange Labs (2026). Original
10. Hollow-LLM Attack: Computationally Trivial Weights in Zero-Knowledge Verification of LLM Inference, C. Gong et al. (2026). Original
11. A System Overview for Near-Term, Low-Trust AI Compute Verification, N. Cankaya (2026). Original
12. Pacing AI Requires Proof, Attestable (2026). Original
13. Timing and Memory Telemetry on GPUs for AI Governance, S. K. Monfared et al. (2026). Original
14. On the Difficulty of Software-Based Attestation of Embedded Devices, C. Castelluccia et al. (2009). Original
15. Refutation of "On the Difficulty of Software-Based Attestation of Embedded Devices", A. Perrig & L. van Doorn (2010). Original