In this Reversible Data Hiding in Encrypted Images by Reversible Image Transformation paper we propose a novel framework for RDH-EI based on RIT. Different from previous frameworks which encrypt a plaintext image into a ciphertext form, RIT-based RDH-EI shifts the semantic of original image to the semantic of another image and thus protect the privacy of the original image. Because the encrypted image has the form of a plaintext image, it will avoid the notation of the curious cloud server and it is free for the cloud sever to choose any one of RDH methods for plaintext images to embed watermark.

We realize an RIT based method by improving the image transformation technique  to be reversible. By RIT, we can transform the original image to an arbitrary selected target image with the same size, and restore the original image from the encrypted image in a lossless way. Two RDH methods including PEE-based RDH and UES are adopted to embed watermark in the encrypted image to satisfy different needs on image quality and embedding capacity.