Which cellular automata rules are suitable for randomizing an input sequence?
Rule 30 is probably the "most random" of all 256 rules. It has been used as random number generator, but there are some issues:


Some initial states will result in repetitive output, which is not what we want from a random number generator. However, given that the automaton is large enough, and that the initial state is itself somewhat random, this shouldn't a problem.
There are better ways to generate random numbers.