High capacity reversible data hiding in encrypted images using block labeling

We propose a method of secure and reversible data hiding in encrypted images which ensures lossless recovery of image contents and data with very high embedding capacity. The proposed reversible data hiding method in encrypted images makes use of median edge detector predictor and Huffman coding for reducing the size of axillary information. The proposed method utilizes the spatial correlation of the image for reserving room for data embedding before encryption. Hiding capacity of each 2 x 2 block in the image is calculated based on the prediction error using the median edge detector. The hiding capacities of adjacent four blocks are labeled using Huffman coding, which reduces the size of the auxiliary information hidden along with secret data embedded in the encrypted image. Proposed method does data hiding without changing the characteristics of encrypted image for ensuring security and recovers data and image contents completely. The experimental results show that the proposed method hides higher payload with an average value of 3.34 bpp which is 25 percentage more than the state of the art methods.