I've been reading some sci-fi and there is a frequent mention of decoding alien signals.
From what i read historically in ww2 for decoding enemy message the allies would transmit fake information and then listen to the enemy communicating that fake messages in encrypted form , this enabled the allies to make sort of a known plaintext attack and in addition they had an idea of the ciphers being used which narrowed down area of effort even more
Now to make this question realistic let's say the message contained information which is intelligible to humans in plain text (say if the aliens were sending encrypted English) then is there a way to decode a encoded signal when you do not know about its purpose or context or cipher?
Say you just received an out of ordinary signal from somewhere in cosmos , with definitely has a pattern indicating intelligent origin but nothing more.
Is it possible to decrypt such a message?
