In this paper, we implement a revised pseudo random bit generator based on a
rule-90 cellular automaton. For this purpose, we introduce a sequence matrix
H_N with the aim of calculating the pseudo random sequences of N bits employing
the algorithm related to the automaton backward evolution. In addition, a
multifractal structure of the matrix H_N is revealed and quantified according
to the multifractal formalism. The latter analysis could help to disentangle
what kind of automaton rule is used in the randomization process and therefore
it could be useful in cryptanalysis. Moreover, the conditions are found under
which this pseudo random generator passes all the statistical tests provided by
the National Institute of Standards and Technology (NIST)Comment: 20 pages, 12 figure
