Separable Reversible Data Hiding Scheme in Homomorphic Encrypted Domain Based on NTRU

NTRU (Number Theory Research Unit) has the characteristics of resistance to quantum computing attacks, fast encryption and decryption, and high security. It is very suitable for wireless confidential data networks and authentication systems. Combined with reversible data hiding technology, a separable reversible data hiding scheme in homomorphic encrypted domain based on NTRU is proposed. The image owner directly divides the cover-image into groups of a reference pixel and adjacent pixels. Then, the grouped image is encrypted by NTRU. Finally, the encrypted image is uploaded to the data hider. The encrypted image is divided into groups by the same grouping method as the image owner. After that, the data hider calculates absolute differences of adjacent pixels in each group to obtain histogram of the absolute differences. The additional data can be embedded into the encrypted image by shifting histogram of the absolute differences. After receiving the encrypted image with hidden data, the receiver can either use the data hiding key to directly extract the additional data from encrypted domain to obtain the encrypted image, or use the private key and data hiding key to extract the additional data from plaintext domain to get the cover-image. Experimental results show that our scheme has higher security and better embedding performance comparing with other state-of-the-art works.