Visual cryptography
Author: Monika Agrawal, February 10, 2015 – Posted in: Security – Tags: ,

visual-cryptography
Visual cryptography (VC) was introduced by Moni Naor and Adi Shamir at EUROCRYPT 1994.
Visual cryptography is a cryptographic technique which allows visual information (pictures, text, etc.) to be encrypted in such a way that decryption becomes a mechanical operation that may or may not require a computer.
It is used to encrypt written material (printed text, handwritten notes, pictures, etc) in a perfectly secure way.
OR- Visual Cryptography
Divide image into two parts
Separately, they are random noise
Combination reveals an image
visual-cryptography 01
 k out of n sharing problem
k out of n sharing problem
For a set P of n participants,  a secret image S is encoded into n shadow images called shares (shadows), where each participant in P receives one share.
The original image is visible if any k or more of them are stacked together, but totally invisible if fewer than k transparencies are stacked together.
k out of n example (k=3,n=4)
General k out of k Scheme
In k out of k, the image is visible only if all the shares are stacked together.
If any share in k is lost, and remaining shares are stacked together, it will not form the image.
Thus, in k out of k, all the shares are important
    to construct the image.
 2 out of 2 Scheme (2 subpixels)
visual-cryptography 02
X-OR Visual Cryptography
It is a type of cryptography technique in which we encode image in such a way that we get original image after decoding.It is not possible in normal cryptography technique.Decoding can be done by human visual system or directly with the help of computer

Click here for government certification in Security