A separable reversible data hiding scheme in encrypted image for two cloud servers

This paper presents a separable reversible data hiding in encrypted image (SRDH-EI) based on code division multiplexing (CDM). In this, the owner encrypts the cover image first, and then uploads the preprocessed image to two cloud servers. In the servers, two encrypted pixels, on the same place of uploaded images, form an embedded vector. Finally the secret bits, which are encoded to CDM spreading sequences, are embedded into the vector. At the receiver side, there are three cases: 1) if they only have the data hiding key, the secret bits can be extracted; 2) if they only have the encryption key, the original image can be recovered; 3) if they have the two keys, both of them can be obtained. Compared with the classic dual-images RDH method, the proposed method protects the content security of the outsourced cloud image and has a better performance on visual quality and embedding capacity.