# FLClear: Visually Verifiable Multi-Client Watermarking for Federated Learning

arXiv: https://arxiv.org/abs/2511.12663 · HTML: https://mlsanity.com/paper/2511.12663/

## Key facts

- No citing papers in the map yet (data through 14 Oct 2026).
- Builds on 31 of its 60 references that are in the map.
- First posted on arXiv 16 Nov 2025.

## Builds on (most cited first, 30 of 31)

- [Deep Residual Learning for Image Recognition](https://mlsanity.com/paper/1512.03385/) (2015)
- [Very Deep Convolutional Networks for Large-Scale Image Recognition](https://mlsanity.com/paper/1409.1556/) (2014)
- [Communication-Efficient Learning of Deep Networks from Decentralized Data](https://mlsanity.com/paper/1602.05629/) (2016)
- [Batch Normalization: Accelerating Deep Network Training by Reducing Internal Covariate Shift](https://mlsanity.com/paper/1502.03167/) (2015)
- [MobileNetV2: Inverted Residuals and Linear Bottlenecks](https://mlsanity.com/paper/1801.04381/) (2018)
- [Fashion-MNIST: a Novel Image Dataset for Benchmarking Machine Learning Algorithms](https://mlsanity.com/paper/1708.07747/) (2017)
- [Federated Optimization in Heterogeneous Networks](https://mlsanity.com/paper/1812.06127/) (2018)
- [Learning both Weights and Connections for Efficient Neural Networks](https://mlsanity.com/paper/1506.02626/) (2015)
- [Adaptive Federated Optimization](https://mlsanity.com/paper/2003.00295/) (2020)
- [Measuring the Effects of Non-Identical Data Distribution for Federated Visual Classification](https://mlsanity.com/paper/1909.06335/) (2019)
- [A Survey on Multi-Task Learning](https://mlsanity.com/paper/1707.08114/) (2017)
- [FedBN: Federated Learning on Non-IID Features via Local Batch Normalization](https://mlsanity.com/paper/2102.07623/) (2021)
- [Turning Your Weakness Into a Strength: Watermarking Deep Neural Networks by Backdooring](https://mlsanity.com/paper/1802.04633/) (2018)
- [FedPAQ: A Communication-Efficient Federated Learning Method with Periodic Averaging and Quantization](https://mlsanity.com/paper/1909.13014/) (2019)
- [A survey of deep neural network watermarking techniques](https://mlsanity.com/paper/2103.09274/) (2021)
- [SoK: How Robust is Image Classification Deep Neural Network Watermarking? (Extended Version)](https://mlsanity.com/paper/2108.04974/) (2021)
- [WAFFLE: Watermarking in Federated Learning](https://mlsanity.com/paper/2008.07298/) (2020)
- [FedIPR: Ownership Verification for Federated Deep Neural Network Models](https://mlsanity.com/paper/2109.13236/) (2021)
- [FedTracker: Furnishing Ownership Verification and Traceability for Federated Learning Model](https://mlsanity.com/paper/2211.07160/) (2022)
- [Clustered Vehicular Federated Learning: Process and Optimization](https://mlsanity.com/paper/2201.11271/) (2022)
- [FedCIP: Federated Client Intellectual Property Protection with Traitor Tracking](https://mlsanity.com/paper/2306.01356/) (2023)
- [Who Leaked the Model? Tracking IP Infringers in Accountable Federated Learning](https://mlsanity.com/paper/2312.03205/) (2023)
- [FedRight: An Effective Model Copyright Protection for Federated Learning](https://mlsanity.com/paper/2303.10399/) (2023)
- [BELT: Old-School Backdoor Attacks can Evade the State-of-the-Art Defense with Backdoor Exclusivity Lifting](https://mlsanity.com/paper/2312.04902/) (2023)
- [ModelShield: Adaptive and Robust Watermark against Model Extraction Attack](https://mlsanity.com/paper/2405.02365/) (2024)
- [FedGMark: Certifiably Robust Watermarking for Federated Graph Learning](https://mlsanity.com/paper/2410.17533/) (2024)
- [RobWE: Robust Watermark Embedding for Personalized Federated Learning Model Ownership Protection](https://mlsanity.com/paper/2402.19054/) (2024)
- [Infighting in the Dark: Multi-Label Backdoor Attack in Federated Learning](https://mlsanity.com/paper/2409.19601/) (2024)
- [Harmless Backdoor-based Client-side Watermarking in Federated Learning](https://mlsanity.com/paper/2410.21179/) (2024)
- [Exploring Federated Learning Dynamics for Black-and-White-Box DNN Traitor Tracing](https://mlsanity.com/paper/2407.02111/) (2024)

## Abstract (arXiv)

Federated learning (FL) enables multiple clients to collaboratively train a shared global model while preserving the privacy of their local data. Within this paradigm, the intellectual property rights (IPR) of client models are critical assets that must be protected. In practice, the central server responsible for maintaining the global model may maliciously manipulate the global model to erase client contributions or falsely claim sole ownership, thereby infringing on clients' IPR. Watermarking has emerged as a promising technique for asserting model ownership and protecting intellectual property. However, existing FL watermarking approaches remain limited, suffering from potential watermark collisions among clients, insufficient watermark security, and non-intuitive verification mechanisms. In this paper, we propose FLClear, a novel framework that simultaneously achieves collision-free watermark aggregation, enhanced watermark security, and visually interpretable ownership verification. Specifically, FLClear introduces a transposed model jointly optimized with contrastive learning to integrate the watermarking and main task objectives. During verification, the watermark is reconstructed from the transposed model and evaluated through both visual inspection and structural similarity metrics, enabling intuitive and quantitative ownership verification. Comprehensive experiments conducted over various datasets, aggregation schemes, and attack scenarios demonstrate the effectiveness of FLClear and confirm that it consistently outperforms state-of-the-art FL watermarking methods.