  Reversible data hiding in encrypted images is an effective technology for
data hiding and protecting image privacy. Although there are many high-capacity
methods have been presented in recent year, most of them need a pre-processing
phase to reserve room in the original image before encryption. It may be
unpractical, because the image provider has to analyze the content of the image
and accomplish additional operations. In this paper, we propose a new robust
vacate room after encryption schema based on polynomial arithmetic, which
achieves a high embedding capacity with the perfect recovery of the original
image. An efficient symmetric encryption method is applied to protect the
privacy of the original image. One polynomial is generated by the encryption
key and a group of the encrypted pixel, and the secret data is mapped into
another polynomial. Through the arithmetic of these two polynomials, we can
extract secret data and recover origin image, separately. Experimental results
demonstrate that our solution has a stable and good performance on various
images (include rough texture image). Compared with some typical methods, the
proposed method can get better decrypted image quality with a large embedding
capacity.
