A Visual Cryptography Scheme for Secret Hiding using Pre-Processing

Visual cryptography is a cryptographic technique in which an image (secret) is encrypted using shares of the image and then those shares at the receiver side are overlapped to decrypt the original secret. The advantage of such a process is that no high computation power is needed to decrypt the secret. However, the ease of working reduces the overall security of the system. Any individual to whom the secret is not directed can intercept the shares and look at the secret. Another disadvantage of such a system is, reduction of image quality (contrast) at the receiver. In this paper, we introduce a new algorithm which handles the above mentioned cons. The secret is perfectly encrypted and then overlapped on hiding image (overlap image). The secret image is encrypted using very low complex computation which makes it easier to use and implement. Image contrast is not distorted at the receiver and the secret is well encrypted which disables any interceptor to decode the secret even if he intercepts all the shares. The algorithm also introduces the concept of keys which are used to increase the overall security of the system. Another advantage of this system is not having multiple images to hide the shares.