Design of pseudo random keystream generator using fractals

This paper presents a novel method for designing a pseudo random keystream generator (PRKG) based on fractal images. Although a fractal image has high correlation between its pixels, the proposed technique succeeds in almost eliminating this correlation and the output stream passes the NIST statistical test suite. The post-processing on the fractals is based only on a confusion process and uses a nonlinear network with a delay block to randomize the output stream. Many statistical measures and the NIST suite have been used to evaluate the processed fractals and the results are promising. As an example to validate the PRKG, the output stream is used in a simple image encryption system. The encrypted image is tested by calculating pixel correlations, differential attack measures, entropy and it also passes the NIST test suite.