Background: Medical image authentication is an important area which attempts to establish
ownership authentication and data authentication of medical images.
Aims: In this paper, we propose a new reversible watermarking scheme based on a novel half difference
expansion technique for medical image forensics.
Methods: Conventional difference expansion based reversible watermarking scheme generates watermarked
images with less visual quality, and the embedding rate was considerably less due to the
high probability of overflow or underflow. In the proposed scheme, the quality of the watermarked
image has been improved by modifying the traditional difference expansion based watermarking
scheme, half of the difference between two pixels will be expanded during watermarking. The
modification of pixels during watermarking is limited by expanding half of the pixel difference,
which helps to obtain watermarked images with better visual quality and improved embedding rate
due to less chance of overflow or underflow during watermarking. We also propose a tamper detection
localization process to detect the tampered regions from the watermarked image.
Results: Experimental study of the proposed scheme on the standard medical images from Osrix
medical image data set shows that the proposed watermarking scheme outperforms the existing
schemes in terms of visual quality of the watermarked image and embedding rate.
Conclusion: The overhead related to location map and parity information need to be addressed in
future works to improve the proposed scheme.