Reversible Data Hiding in Encrypted Images with Adaptive Multi-Directional MED and Huffman Code Based on Interval-Wise Dynamic Prediction Axes

With the popularization of digital information, reversible data hiding in ciphertext has become a critical research focus in privacy protection in cloud storage. A reversible data hiding method for encrypted images is proposed: Reversible Data Hiding in Encrypted Images with Adaptive Multi-directional MED and Huffman Code based on Interval-Wise Dynamic Prediction Axes (RDHEI-AHIDA). Firstly, the original image is predicted by the gradient Adaptive Multi-Directional Median Edge Detector (AM-MED) to obtain the critical gradient and the position of the Interval-wise Dynamic Prediction Axes (IDP-Axes). Then, information bits are allocated at intervals on the IDP-Axes. Combining the determined position of the IDP-Axes and the critical gradient, the prediction error values of the original image are calculated and recorded. After the image is encrypted, according to the distribution of prediction error values, an adaptive Huffman code rule is established, and pixel marking, classification and auxiliary information embedding are carried out. Finally, the secret data is embedded by the bit replacement method. Compared with the state-of-the-art RDHEI methods, experimental results show that RDHEI-AHIDA not only provides a higher pure payload while ensuring security but also exhibits certain robustness.