Visual cryptography

Visual cryptography allows information that is available in the form of white and black pixels to be encrypted. The decryption can take place solely with the aid of optical perception, in particular the help of computers is not required.

The first visual encryption method was developed in 1994 by Moni Naor and Adi Shamir . It is a visual secret sharing technique in which an image is broken down into partial images. Any number of partial images does not allow any conclusions to be drawn about the original. Each partial image is printed on a transparent film. The decryption takes place by superimposing all parts. ${\ displaystyle n}$ ${\ displaystyle n-1}$

example

Demonstration of visual cryptography

In this example, the Wikipedia logo is split into two slides.

For each white pixel of the logo, two identical blocks of four pixels are created on the film, half of which contain black and half white pixels. If you put the blocks on top of each other, a gray block is created (viewed from a distance) .
Two complementary blocks of four are generated for each black pixel . If you put the blocks on top of each other, a black block is created.

If each pixel of the original image is encoded randomly as described above, each slide is in itself a random collection of blocks. Information about the original can only be obtained by knowing both slides.

Individual evidence

↑ Moni Naor and Adi Shamir, Visual Cryptography, EUROCRYPT 1994, pp. 1-12

Web links

[1] Moni Naor and Adi Shamir, Visual Cryptography, EUROCRYPT 1994, pp. 1-12