A reversible crypto-watermarking system for secure medical image transmission

Health care institution demands exchange of medical images of number of patients to sought opinions from different experts. In order to reduce storage and secure transmission of the medical images, the paper presents a reversible crypto-watermarking technique. The system is based on stream cipher encryption of the image using a secret key and the secret key ciphering is done by public-private key crypto system-ELGamal. The secret key which is encrypted using ELGamal and is watermarked in Discrete Cosine Transform (DCT) domain using the spread spectrum coding algorithm. The Digital Watermarking is the process of embedding data to multimedia content. This can be done in spatial as well as frequency domain of the cover image to be transmitted. The robustness against attacks is ensured while embedding the encrypted secret key in transform domain. But if capacity is the major concern then spatial pixel manipulations based on prediction errors can be effective media for transferring the data. The experimental results reveals and analyzes the reversible crypto-watermarking method in terms of PSNR value, entropy requirements and histogram analysis.