A Reversible-Zero Watermarking Scheme for Medical Volume Data via Difference Expansion

Today, advances in medical technologies extensively utilize 3D volume data for accurate and efficient diagnostics. However, sharing these data across networks in telemedicine poses significant security risks of data tampering and unauthorized copying. To address these challenges, this paper proposes a novel reversible-zero watermarking approach, termed VolMark, for medical volume data to protect their ownership and authenticity in telemedicine. The proposed Vol-Mark method offers two key benefits: 1) it preserves the accuracy of medical volume data by embedding a reversible watermark that can be removed losslessly, and 2) it enables continuous ownership verification through the zero-watermarking technique even after watermark removal. To achieve this, we introduce a novel cubic difference expansion (c-DE) method specifically designed for volume data. By combining c-DE with the 3D integer wavelet transform, the proposed Vol-Mark ensures reversibility without compromising data integrity, while also improving the reliability of the watermark. Additionally, Vol-Mark incorporates a zerowatermark using 3D DNN-based feature extraction to better capture the properties of volume data, along with an encryption mechanism based on the Henon map to enhance security. Comprehensive experimental results demonstrate the effectiveness of the proposed method, highlighting its strong robustness against both conventional and geometric attacks in medical volume data.