Real-time reversible data hiding in encrypted images based on hybrid embedding mechanism

In this paper, we propose a novel real-time scheme of separable reversible data hiding in encrypted images, which consists of image encryption, data embedding, data extraction and image recovery. In image encryption phase, the content owner divides the original image into a number of non-overlapping blocks and encrypts blocks by stream cipher and permutation. During the data embedding phase, the data hider classifies encrypted blocks into smooth region and complex region according to the threshold and replaces the MSB layer of a part of pixels in blocks of smooth region with the secret data. Then, the LSB layers of other pixels are collected and compressed to generate a room for embedding the secret data again. When the receiver receives the marked image, he can divide the marked image into blocks and decrypt them by the encryption key to obtain a similar image with good quality. If the receiver only has the data hiding key, he can classify the blocks into smooth region and complex region according to the threshold and extract the embedded data by the data hiding key. If the receiver has both encryption key and data hiding key, he can extract the embedded data from the marked image and recover the original image perfectly. The proposed scheme can achieve satisfactory quality of decrypted image and high embedding rate. Experimental results demonstrate the effectiveness and computational efficiency of our scheme.