An a Priori and a Posteriori Protection by Means of Data Hiding of Encrypted Images: Application to Ultrasound Images

Abstract

In this paper, we propose a novel scheme which allows embedding a message, a set of security attributes, into encrypted images. This message can be accessed whether the image is encrypted or not for the purpose of verifying the reliability of images. The proposed solution relies on the insertion into the image of a predefined watermark, a “pre-watermark”, before the encryption process. Message insertion and extraction are then conducted into the encrypted image. It is the impact of this data hiding process onto the “pre-watermark” that gives us access to the message after the image has been decrypted. The proposed scheme has been implemented considering the RC4 stream cipher algorithm and the Least Significant Bit substitution watermarking method. Experimental results achieved on 8 bit depth ultrasound images demonstrate the capability of our system to make available security attributes in both spatial and encrypted domains while minimizing image distortion.