(2, N) Visual Cryptography Sharing Case
Sharing a secret with an arbitrary number of people N such that at least 2 of them are required to decode the secret is one form of the visual secret sharing scheme presented by Moni Naor and Adi Shamir in 1994. In this scheme we have a secret image which is encoded into N shares printed on transparencies. The shares appear random and contain no decipherable information about the underlying secret image, however if any 2 of the shares are stacked on top of one another the secret image becomes decipherable by the human eye.
Every pixel from the secret image is encoded into multiple subpixels in each share image using a matrix to determine the color of the pixels. In the (2,N) case a white pixel in the secret image is encoded using a matrix from the following set:
{all permutations of the columns of} : 
While a black pixel in the secret image is encoded using a matrix from the following set:
{all permutations of the columns of} : 
For instance in the (2,2) sharing case (the secret is split into 2 shares and both shares are required to decode the secret) we use complimentary matrices to share a black pixel and identical matrices to share a white pixel. Stacking the shares we have all the subpixels associated with the black pixel now black while 50% of the subpixels associated with the white pixel remain white.
Read more about this topic: Visual Cryptography
Famous quotes containing the words visual, sharing and/or case:
“I may be able to spot arrowheads on the desert but a refrigerator is a jungle in which I am easily lost. My wife, however, will unerringly point out that the cheese or the leftover roast is hiding right in front of my eyes. Hundreds of such experiences convince me that men and women often inhabit quite different visual worlds. These are differences which cannot be attributed to variations in visual acuity. Man and women simply have learned to use their eyes in very different ways.”
—Edward T. Hall (b. 1914)
“The traditional American husband and father had the responsibilities—and the privileges—of playing the role of primary provider. Sharing that role is not easy. To yield exclusive access to the role is to surrender some of the potential for fulfilling the hero fantasy—a fantasy that appeals to us all. The loss is far from trivial.”
—Faye J. Crosby (20th century)
“Rhetoric may be defined as the faculty of observing in any given case the available means of persuasion.”
—Aristotle (384–323 B.C.)