Paper 2026/1380

TIM: A Sensitive-Parameter-Privacy Blind Watermarking Based on Zero-Knowledge Proof

Abstract

Blind watermarking enables image ownership verification without requiring the original image. However, existing schemes usually require the owner to reveal the watermark seed and watermark positions during extraction. This creates a strong trust assumption on the verifier. Once such secrets are exposed, a malicious verifier can forge or remove the watermark. In this paper, we present TIM, the first publicly verifiable blind watermarking scheme with sensitive parameters privacy based on zero-knowledge proof. TIM reconstructs the extraction procedure of Integer DCT blind watermarking into an arithmetic-circuit-friendly form. This allows the owner to prove correct extraction without revealing the watermark seed or embedding positions. TIM addresses three main challenges. The first is the high proving cost for high-resolution images. The second is the conflict between circuit rigidity and watermark robustness. The third is the hashing overhead of iterative state binding. To address them, TIM combines Nova and Spartan to decompose full-image extraction into iterative proofs. It uses a threshold-based voting mechanism for robust detection. It also introduces a hierarchical state update mechanism to reduce circuit and memory costs. Experiments show that TIM preserves good imperceptibility and robustness while achieving practical efficiency. For a 4K image, proof generation takes 5.61 minutes and uses 9.61 GB peak memory. These results show that TIM is the first blind watermarking scheme to achieve seed privacy, public verifiability, and practical performance for high-resolution image ownership proofs.