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Encrypting Pictures Using Chaotic Cellular Automata

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3-D cellular automaton

Researchers are using a cellular automaton to generate a pseudorandom signal that makes the grid-like array (shown here in 3D) look like noise.

Credit: Wikipedia

Marina Jeaneth Machicao and colleagues at the University of San Paul in Brazil are using chaos to encrypt images. Their approach generates a pseudo-random signal via a cellular automaton, a grid-like array in which each cell can be either black or white at any instant, and in the next step each square would change according to a predetermined rule and the color of the square around it.

Using standard statistical tests known as ENT and DIEHARD, the team found that Fredkin B1357/S02468 delivered the most consistent results in making the grid look like noise. The researchers note that the output of this automata is precisely determined by its starting state, which can act as a password. The automata can be freely distributed so that anyone can use it, but only a person with the password can decrypt any given message. The password is entered to produce a starting pattern of cells in the cellular automaton, and a pseudo-random output is generated by running through 20 million iterations.

The output is superimposed on the picture intended for encryption. After the picture is sent, the receiver with the correct password can view the image by carrying out the procedure in reverse.

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