  This work proposes an improved reversible data hiding scheme in encrypted
images using parametric binary tree labeling(IPBTL-RDHEI), which takes
advantage of the spatial correlation in the entire original image but not in
small image blocks to reserve room for hiding data. Then the original image is
encrypted with an encryption key and the parametric binary tree is used to
label encrypted pixels into two different categories. Finally, one of the two
categories of encrypted pixels can embed secret information by bit replacement.
According to the experimental results, compared with several state-of-the-art
methods, the proposed IPBTL-RDHEI method achieves higher embedding rate and
outperforms the competitors. Due to the reversibility of IPBTL-RDHEI, the
original plaintext image and the secret information can be restored and
extracted losslessly and separately.
