(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:
“Unlike any other visual image, a photograph is not a rendering, an imitation or an interpretation of its subject, but actually a trace of it. No painting or drawing, however naturalist, belongs to its subject in the way that a photograph does.”
—John Berger (b. 1926)
“To see ourselves as others see us can be eye-opening. To see others as sharing a nature with ourselves is the merest decency. But it is from the far more difficult achievement of seeing ourselves amongst others, as a local example of the forms human life has locally taken, a case among cases, a world among worlds, that the largeness of mind, without which objectivity is self- congratulation and tolerance a sham, comes.”
—Clifford Geertz (b. 1926)
“It was a maxim with Mr. Brass that the habit of paying compliments kept a man’s tongue oiled without any expense; and that, as that useful member ought never to grow rusty or creak in turning on its hinges in the case of a practitioner of the law, in whom it should be always glib and easy, he lost few opportunities of improving himself by the utterance of handsome speeches and eulogistic expressions”
—Charles Dickens (1812–1870)