  While the existing vacating room before encryption (VRBE) based schemes can
achieve decent embedding rate, the payloads of the existing vacating room after
encryption (VRAE) based schemes are relatively low. To address this issue, this
paper proposes a generalized framework for high-capacity RDHEI for both VRBE
and VRAE cases. First, an efficient embedding room generation algorithm (ERGA)
is designed to produce large embedding room by using pixel prediction and
entropy encoding. Then, we propose two RDHEI schemes, one for VRBE, another for
VRAE. In the VRBE scenario, the image owner generates the embedding room with
ERGA and encrypts the preprocessed image by using the stream cipher with two
encryption keys. Then, the data hider locates the embedding room and embeds the
encrypted additional data. In the VRAE scenario, the cover image is encrypted
by an improved block modulation and permutation encryption algorithm, where the
spatial redundancy in the plain-text image is largely preserved. Then, the data
hider applies ERGA on the encrypted image to generate the embedding room and
conducts data embedding. For both schemes, the receivers with different
authentication keys can respectively conduct error-free data extraction and/or
error-free image recovery. The experimental results show that the two proposed
schemes outperform many state-of-the-art RDHEI arts. Besides, the schemes can
ensure high security level, where the original image can be hardly discovered
from the encrypted version before and after data hiding by the unauthorized
user.

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