A high payload separable reversible data hiding in cipher image with good decipher image quality

Reversible Data Hiding (RDH) is a technique that is used to protect the secret by using digital cover media to hide it and to retrieve the cover after extracting the secret. The Reversible Data Hiding In an Encrypted Image (RDHIEI) protects the privacy of secret information and also the cover by hiding confidential information in a cipher image. Some of the algorithms in RDHIEI can extract the information if and only if the cipher image is already decrypted and some algorithms can decrypt the image if only if the data has already been extracted from the cipher image. In those algorithms, the extraction and decryption cannot be separated. But some applications like healthcare and army image processing require that image recovery and information extraction to be separate processes; this new technique is called Separable Reversible Data Hiding In an Encrypted Image (SRDHIEI). In this paper, a novel SRDHIEI is suggested with high payload and good quality decipher image by embedding information in a cipher image on two levels. In the first level data is embedded by the Least Significant Bit(LSB) substitution method and in the second level data is embedded by using Pixel Expansion (PE) method. For image confidentiality, the cover image is encrypted by using an additive homomorphism technique. The benefits of the proposed method is to transfer the cover image in an extremely secure manner with PSNR of 8.6813 dB, -0.0077 correlation and 7.998 entropy. The average embedding capacity of the proposed method is 217579 bits, and the decrypted image PSNR is 29.5 dB. 100% restoration of the host image and 100% lossless secret information extraction can be achieved.