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.
Everyone makes the assumption that ‘aliens’ have a spoken language.
Is there any cursive on the Voyager probe?
Couldn’t resist the attempt at humor.