Difference expansion based Reversible Data Hiding for medical images

Reversible Data Hiding (RDH) is the technique of embedding secret messages into a cover image by modifying its pixel values. In RDH technique, both the embedded message and the cover image are recovered. The Difference Expansion is the high quality reversible method for data embedding. The existing Lee method and Pixel Pair Mapping (PPM) method of difference expansion produced redundant space for data embedding by grouping two columns of pixel values. The modified PPM method combines the techniques of existing Lee method and PPM method and groups any number of columns in the forward direction and groups two columns in the reverse direction similar to PPM method. Difference Pair Mapping (DPM) method along both forward and backward direction is implemented to improve the embedding performance by exploiting the statistical properties of an image using prediction based method with arbitrary threshold. The prediction values of pixel-pairs are responsible for providing security to the message being embedded. The simulation results are produced for the modified PPM method and DPM method along both the direction to show the improvement in the embedding capacity.