Isn't there an element of "natural" encryption here, though?
So far as the aliens are concerned, our signals are in a foreign language -- even if they are not encrypted. And vice versa...
There is a language barrier. So I suppose you could call that natural encryption, but I disagree.
If you got a message from an alien race. You would know it was from an alien race. You might not understand it, but you would know that it wasn’t from Earth. Encryption just keeps the message private. But if an alien race were trying to communicate with us, they would do it in mathematics, or some physics that any intelligent race that could receive the signal could understand. Like the Voyager probe.
What if aliens communicate by colors of light ?
Or by pheromones ?
What if they don’t project their ‘communications’ outward into space ?
Signals follow a pattern. Language doesn’t matter. It’s the pattern that sticks out. It’s how packet analysis can determine the type of information you’re transmitting and receiving without knowing the precise info you’ve got.
Encryption disrupts patterns and can blind snoopers to the content.