Take a look at this document referring to 29 extraterrestrial messages on NSA’s website.
Is this just a fictional exercise to find people good at decrypting things?
Is it disinformation? Perhaps when you decrypt this successfully you will find it is aliens talking about the invasion of Earth, only it’s really the NSA setting the stage for the fake alien invasion which is the next thing that will be used to control use when “terrorism” no longer serves to be a viable control.
Is it perhaps a test just to see how a faction of the populace will respond to the knowledge of extraterrestrials?
Or perhaps it’s genuine, they really haven’t been able to decrypt it with their resources and are hoping that someone else will?