Maybe this is a (very) stupid question, but anyways, I was wondering about that lately just for fun.
So SETI is basically searching (among all the noise coming to use from space) unusual (repeatable) patterns among all the noise from outer-space we capture on Earth.
But what if this is the wrong way to look for possible alien-signals? What if alien (or us, the same thing) know, that another planet (from huge distances) will receive mostly noise (I know, this already contradicts the stuff below, but anyways) and nothing else (so maybe quite impossible to detect any useful signal-pattern).
So, if we consider received noise as highly random, what if aliens transmit on purpose there signal encoded in super-random-way? What I mean to say is what if SETI should look about quite abnormal-randomness (e.g. super random noise) on received signals?
Of course, decoding this super random noise is another question :).