Reversible data hiding in encrypted images by active block exchange and room reservation

Reversible data hiding in encrypted images (RDH-EI) has got some promising applications in cloud storage, medical imaging, forensics etc. It has gained considerable research interest in recent years. In this paper, we follow the paradigm of reserving room for additional data before encrypting the image and propose a new method by classifying the smooth and coarse blocks of the image. LSB-planes of coarse blocks are reserved to hide additional data. Smooth blocks are used to back-up the locations reserved for those additional data, using a traditional RDH technique that works on unencrypted images. Experiments show that proposed method gives superior performance than the state-of-the-art methods and is suitable for applications that demand high data hiding capacity.