Cheat immune visual cryptography for secure transmission of images

Abstract

Transmission of confidential information securely on insecure communication channel is atmost important. Image encryption is a method which is used to hide the secret image. During the course of transmission over insecure communication network, intruders may alter the encrypted data and may result in changing the visual meaning of the image. In this paper, a novel cheat immune image encryption technique is proposed. If a middle man tries to alter the encrypted data than decryption of an image fails. During encryption, it divides the source image into '3' shares and decrypts by superimposing all the 3 shares. In this technique, secret information or image can be retrieved only if all three shares are in possession. The traditional visual cryptographic scheme suffers from the problem of pixel expansion. In this aspect ratio of an image changes resulting in increasing the width of encrypted image. To overcome this, a novel random grid visual cryptography is proposed. The methodology uses Residue Number System (RNS) for encryption and utilizes Mixed Radix Representation(MRR) for decryption. RNS and Mixed radix is mainly used in fault tolerance. This is designed so as to avoid cheating during decryption.