A reversible data hiding scheme for sharing medical data

Abstract

In this paper, we propose a data hiding technique that helps the receiver to extract the secret data and recover the original image. The receiver first creates a pair of keys using Paillier cryptosystem and shares public key with sender. The sender enlarges cover image of size M × N to (2M − 1) × (2N − 1) by inserting one row (column) between two rows (columns), and then divides it into 3 × 3 blocks such that two boundary blocks have a row or a column in common, and two interior blocks have one row and one column in common. The block’s corner pixels, called as seed pixels, belong cover image and others, called as non-seed pixels, are initialized as 1 that are updated while embedding secret data in seed pixels. The block’s central pixels hide a secret bit using the parity and seed pixels are processed clockwise to hide two secret bits in each using separate procedures for even and odd pixels. The seed’s next pixel is multiplied by a fixed number that helps receiver to determine how it was processed at sender side. All pixels are encrypted using Paillier public key, giving a stegoimage, that is transmitted to the receiver. The receiver decrypts the stegoimage using Paillier private key, extracts the secret data and cover image by performing the data extraction process. The embedding rate of proposed method is 2.24 bits per pixel, which is 12 %, 16 %, 89 %, 83 %, 114 %, better than the Bhardwaj, Wang et al., Chen-Chang, Chi et al., Liu et al., respectively.