Recognition: unknown
COPYCOP: Ownership Verification for Graph Neural Networks
Pith reviewed 2026-05-08 16:14 UTC · model grok-4.3
The pith
CopyCop detects whether one GNN is a copy of another even after the adversary changes its architecture, weights, embedding dimension, and output transformations.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Given two GNNs that output node embeddings, CopyCop determines if they were trained independently or if one is an adversarial copycat that may differ in architecture, weights, and embedding dimension and whose outputs may have been transformed. It supplies theoretical guarantees for this detection and, in experiments on 14 datasets with 5 GNN architectures, proves accurate and robust against a broad class of adversarial attacks and transformations.
What carries the argument
CopyCop algorithm that locates a detectable invariant preserved in the embedding spaces of copycat GNNs despite architectural differences and output transformations.
If this is right
- GNN owners gain a practical way to verify ownership against disguised copies.
- Existing watermarking and fingerprinting techniques are shown to be insufficient under the stated adversarial conditions.
- Theoretical guarantees accompany the detection decisions.
- The method works across multiple datasets and GNN architectures while resisting broad adversarial transformations.
Where Pith is reading between the lines
- The same invariant-based idea could be tested on non-graph neural networks that produce embeddings.
- Detection thresholds might be tuned per domain to balance false positives and missed copies.
- The approach could support automated monitoring of public model repositories for unauthorized derivatives.
Load-bearing premise
There exists a detectable invariant in the embedding spaces of independently trained versus copycat GNNs that survives arbitrary transformations and architectural differences.
What would settle it
A concrete case in which CopyCop fails to flag a known transformed copycat GNN or incorrectly flags two independently trained GNNs as copies.
Figures
read the original abstract
Given two GNNs that output node embeddings, how can we determine if they were trained independently? An adversary could have trained one GNN specifically to mimic the other GNN's embeddings. To obscure this relationship between the GNNs, the adversarial GNN might then transform its output embeddings. The two GNNs could have different architectures, weights, and embedding dimensions, and the adversary can transform the embeddings. Despite these stringent conditions, our algorithm (named CopyCop) can identify such copycat GNNs, unlike existing watermarking and fingerprinting methods. We also provide theoretical guarantees for CopyCop. Finally, experiments on 14 datasets and 5 GNN architectures demonstrate that CopyCop is accurate and robust against a broad class of adversarial attacks and transformations. Code is available at: https://anonymous.4open.science/r/CopyCop-Graph-Ownership-Verification-8143/README.md
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper introduces COPYCOP, an algorithm for determining whether two GNNs that produce node embeddings were trained independently or whether one is an adversarial copycat of the other. The method is claimed to succeed even when the models differ in architecture, weights, and embedding dimension and when the adversary applies arbitrary transformations to the output embeddings to obscure the relationship. Unlike prior watermarking or fingerprinting approaches, COPYCOP is presented as relying on an invariant detectable in the embedding spaces; the manuscript asserts theoretical guarantees for this detection and reports empirical accuracy and robustness across 14 datasets and 5 GNN architectures.
Significance. If the central claim holds, COPYCOP would provide a watermark-free, transformation-robust method for GNN ownership verification, addressing a practical need in intellectual-property protection for graph models. The availability of code and the breadth of the experimental evaluation (14 datasets) are positive features that would facilitate reproducibility and further testing.
major comments (3)
- [Abstract] Abstract: the claim of 'theoretical guarantees' for identifying copycat GNNs under differing architectures, weights, dimensions, and adversarial transformations is asserted without any outline of the proof strategy, key assumptions, or lemmas. This is load-bearing because the central claim rests on the existence of a detectable invariant that survives the stated conditions; without the derivation, the scope and tightness of the guarantees cannot be assessed.
- [Experiments] Experimental evaluation: the robustness claims against 'a broad class of adversarial attacks and transformations' on 14 datasets are presented without error bars, statistical significance tests, or explicit definitions of the attack models and transformation families. This undermines verification of the empirical support for the claim that COPYCOP succeeds where watermarking and fingerprinting fail.
- [Method] Method description: the concrete form of the invariant extracted from node embeddings (and the procedure for comparing two embedding spaces of possibly different dimensions) is not specified with sufficient detail to allow independent reproduction or to check whether it reduces to a self-defined quantity under the adversary's transformations.
minor comments (1)
- [Code availability] The code repository link is provided, which is helpful; however, the README should include explicit instructions for reproducing the 14-dataset experiments and the exact attack configurations used.
Simulated Author's Rebuttal
We thank the referee for their constructive and detailed review of our manuscript. We address each major comment point by point below, agreeing where revisions are warranted to strengthen clarity, reproducibility, and empirical rigor.
read point-by-point responses
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Referee: [Abstract] Abstract: the claim of 'theoretical guarantees' for identifying copycat GNNs under differing architectures, weights, dimensions, and adversarial transformations is asserted without any outline of the proof strategy, key assumptions, or lemmas. This is load-bearing because the central claim rests on the existence of a detectable invariant that survives the stated conditions; without the derivation, the scope and tightness of the guarantees cannot be assessed.
Authors: We agree that the abstract would benefit from a concise outline of the theoretical contributions to allow readers to better assess the scope of the guarantees. The guarantees (detailed in Section 3) establish the existence of an invariant in the embedding spaces that distinguishes independently trained models from copycats, even under architectural differences, dimension mismatches, and adversarial transformations. We will revise the abstract to briefly mention the high-level proof strategy, key assumptions (e.g., regarding the class of transformations), and main lemmas. revision: yes
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Referee: [Experiments] Experimental evaluation: the robustness claims against 'a broad class of adversarial attacks and transformations' on 14 datasets are presented without error bars, statistical significance tests, or explicit definitions of the attack models and transformation families. This undermines verification of the empirical support for the claim that COPYCOP succeeds where watermarking and fingerprinting fail.
Authors: We appreciate this feedback on the presentation of the experimental results. While the evaluation covers 14 datasets and 5 architectures with reported accuracy and robustness, we acknowledge that error bars, statistical tests, and explicit attack definitions would improve verifiability. In the revised manuscript, we will add standard deviation error bars across multiple runs, include statistical significance tests (such as paired t-tests against baselines), and provide precise definitions of the attack models and transformation families (e.g., rotations, scalings, noise injections, and other linear/non-linear mappings) in the experimental setup. revision: yes
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Referee: [Method] Method description: the concrete form of the invariant extracted from node embeddings (and the procedure for comparing two embedding spaces of possibly different dimensions) is not specified with sufficient detail to allow independent reproduction or to check whether it reduces to a self-defined quantity under the adversary's transformations.
Authors: We agree that the method section requires greater specificity for independent reproduction and to demonstrate that the invariant does not trivially collapse under adversarial transformations. We will expand this section with additional mathematical detail on the invariant derived from the node embeddings, the exact procedure for aligning and comparing embedding spaces of differing dimensions, algorithmic steps (including pseudocode), and explicit analysis showing robustness to the stated transformations. revision: yes
Circularity Check
No circularity in derivation chain
full rationale
The provided abstract and description introduce COPYCOP as an algorithm that identifies copycat GNNs via detectable invariants in embeddings, supported by theoretical guarantees and experiments across 14 datasets and 5 architectures. No equations, parameter-fitting steps, self-definitional reductions, or load-bearing self-citations are described that would make any prediction or guarantee equivalent to its inputs by construction. The central claim rests on the existence of a transformation-robust invariant, presented as independently verifiable rather than derived from fitted quantities or prior author results in a circular manner. This is a standard non-finding for a methods paper whose core contribution is algorithmic and empirical.
Axiom & Free-Parameter Ledger
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discussion (0)
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