Separable reversible data hiding in homomorphic encrypted domain using POB number system

In this paper, a novel separable reversible data hiding in homomorphic encrypted images (RDHEI) using POB number system is proposed. The frame of the proposed RDHEI includes three parties: content owner, data hider, and receiver. The content owner divides original image contents into a series of non-overlapping equal-size 2 x 2 blocks, and encrypts all pixels in each block with the same key. The encryption process is carried out in an additive homomorphism manner. The data hider divides the encrypted images into the same size blocks as the encryption phase, and further categories all of the obtained blocks into two sets according to the corresponding block entropy. The embedding processes of the two sets are performed through utilizing permutation ordered binary (POB) number system. For the set with smaller entropies, all pixels in addition to the first pixel in each block are compressed by the POB number system; for the set with larger entropies, only u LSBs of all pixels are compressed in order to vacate room for embedding. The receiver can conduct image decryption, data extraction, and image reconstruction in a separable manner. Experimental results verify the superiority of the proposed method.

Automated summary

This paper proposes a separable reversible data hiding method in homomorphic encrypted images using POB number system, involving three parties: content owner, data hider, and receiver. The method divides encrypted images into blocks based on block entropy, compressing pixels in different ways for embedding based on their entropy levels. The receiver can decrypt the image, extract data, and reconstruct the image separately, with experimental results demonstrating the superiority of the proposed method.