基于自适应MSB与差值预测的大容量密文域可逆信息隐藏算法

为提高密文域可逆信息隐藏（reversible data hiding in encrypted images，RDH-EI）的嵌入容量，提出了一种基于自适应MSB（most significant bit）与差值预测的RDH-EI方案。首先将图像进行分块，然后进行块级加密和置乱以抵抗对于加密图像的分析。在嵌入数据阶段，对于自适应MSB预测的方法进行改进，将没有嵌入数据的块，利用部分块内像素之间差值很小的特点采用自适应差值预测的方法嵌入数据，以块中左上角像素为目标像素，用于预测其他像素从而腾出更多的嵌入空间。实验结果表明，所提方法具有可逆性和可分离性，并且在自适应MSB预测方法的基础上进一步提高了嵌入容量，对于512×512大小的灰度图像，平均嵌入容量提高了大约7 445 bit。

High capacity reversible data hiding algorithm in encrypted image based on adaptive MSB and difference prediction

To improve the embedding capacity of reversible data hiding in encrypted images(RDH-EI), this paper proposed an RDH-EI scheme based on adaptive MSB(most significant bit) and difference prediction. Firstly, it divided the image into blocks, and then performed block-level encryption and scrambling to resist the analysis of the encrypted image. In the stage of embedding data, it improved the method of adaptive MSB prediction. For the block without embedded data, the difference between pixels in some blocks was very small, this scheme adopted the method of adaptive difference prediction to embed data, and used the pixel in the upper left corner of the block as the target pixel to predict other pixels so as to make more embedded space. The experimental results show that the proposed scheme has reversibility and separability, and further improves the embedding capacity based on the adaptive MSB prediction method. For 512×512 grayscale images, the increased average embedded capacity is approximately 7 445 bit.