Reversible Data Hiding in Encrypted Images: A Critical Review

The global digital revolution has made this earth more comfortable and smart. This has inspired many engineers to design smart applications in every sphere of modern life. The dark side of the coin is the security of the data. This has motivated technical research in the direction of efficient and hi fi tempered proof data hiding. The most popular technique is reversible data hiding (RDH). The other common name for this method is lossless data hiding. The world technical community is busy publishing the research papers on RDH. There is an ample of scope for developing software tools, which can support image steganography, combined with text encryption. The data is hidden behind some digital cover media. This media can be an image, video, audio or text. The hidden data is transmitted over some channel and it may contain some secret key. This key ensures the authenticated delivery of the payload. The receiver gets the original data after the separation of the same from the actual media. The RDH method helps to recover the original hidden message from the digital data. This method is lossless and this quality is suitable for real life applications like medical science, defence, big data storage etc. The cloud storage can be useful for secured data storage like drop box and google drive. The RDH is used in encrypted images in these applications. The variations in the method can be with and without pre-processing the encrypted images (RDHEI). In this paper, the most common methods of hiding the encrypted images have been reviewed. There are few methods, which allow large data embedding and very efficient while other are not so efficient. The few algorithms discussed are able to provide the lossless data hiding while few have partial distortions. The methods covered are having their own merits and demerits. The better combination is reversible data hiding and lossless recovery of the original carrier and data in encrypted image. The embedding pixels are randomly chosen. The secret key makes it more secure. The random selection of the embedding pixels makes it very difficult to intrude into the communication channel. The secret key at the receiving end opens the lock and the hidden data can easily be recovered without distorting the carrier data. On the basis of the analysis of the entire research papers the unique reversible data hiding method using histogram shifting –imitated approach. The image is broken into finite number of segments and one segment is chosen to hide the data. Each segment is represented in the form of histogram. The peak points are chosen on the basis of intensity of the pixel value. The secret data is hidden into the cover image by modifying the peak point pixel value in the same segment. This embedding method yields high embedding capacity and robust data security.