关键词: 密文医学图像, 可逆信息隐藏, 图像恢复

Abstract: According to the existing algorithm’s low embedding capacity and unstable for medical image, a novel reversible data hiding method in encrypted medical images based on Slash grouping and gradient operator is proposed. After encrypting the medical image by bitwise exclusive-or operator, the encrypted image is divided into blocks and each block contains four specific groups. Then each block embeds two bits by flipping three LSBs of corresponding group. With an encrypted medical image containing additional data, it is firstly decrypted using the encryption key. Then the image recovery and data extraction can be achieved according to the data-hiding key and the gradient operator. The experimental results show that the original medical image can be perfectly recovered and the embedded data can be successfully extracted. When the block size is the same, the proposed method offers better embedding capacity, higher PSNR and lower extracted-bit error rate.

Key words: encrypted medical images, reversible data hiding, image recovery