Watermarking as a Learned Intrinsic Property of Diffusion Models

Recent advances in latent diffusion models have enabled high-quality image generation, but also raise critical concerns for intellectual property protection in model distribution scenarios, where downstream users have unrestricted access to models, allowing arbitrary modifications. Existing watermarking methods either rely on inference-time control of inputs (e.g., specific prompts or noise initialization) or embed watermark signals in auxiliary components, making them easily removable in such settings. In this paper, we propose INMARK, which treats watermarking as an intrinsic property learned by the model. Instead of relying on input control or auxiliary watermarking components, INMARK enables the core denoising network to internalize and reproduce watermark patterns. Extensive experiments demonstrate that INMARK achieves strong generation fidelity, high watermark detectability, and robustness against attacks, while remaining fully compatible with standard diffusion training pipelines. Our results highlight a new perspective on diffusion model watermarking: the denoising network can learn a reliable and persistent watermarking capability, which is crucial in practical model distribution scenarios.