Visual Cryptography

Visual Cryptography is a special encryption technique to hide information in images in such a way that it can be decrypted by the human vision if the correct key image is used. The technique was proposed by Naor and Shamir in 1994. Visual Cryptography uses two transparent images. One image contains random pixels and the other image contains the secret information. It is impossible to retrieve the secret information from one of the images. Both transparent images or layers are required to reveal the information. The easiest way to implement Visual Cryptography is to print the two layers onto a transparent sheet. When the random image contains truely random pixels it can be seen as a One-time Pad system and will offer unbreakable encryption. In the overlay animation you can observe the two layers sliding over each other until they are correctly aligned and the hidden information appears. To try this yourself, you can copy the example layers 1 and 2, and print them onto a transparent sheet or thin paper. Always use a program that displays the black and white pixels correctly and set the printer so that all pixels are printed accurate (no diffusion or photo enhancing etc). You can also copy and past them on each other in a drawing program like paint and see the result immediately, but make sure to select transparent drawing and align both layers exactly over each other.

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Posted: June 28th, 2010
at 7:55pm by Koookiecrumbles


Categories: security

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