This is a bit old, but I have to jump in here.
Apperently, there is a work of art named Kryptos in the courtyard of the CIA's public office, the artwork has an engraved message with a horribly complex code. and the decoded message is stored in the safe of head of the CIA; last I heard is hasn't been solved (probably due to the small sample size)
I'd like to see the creation of the encoding used for the message; so that I not only know the message, but how to decode it; in order to awe and amaze some of the best codebreakers in the world.
The sculpture exists, I don't think that's where the message is actually stored, but there were precautions taken such that when the original creator dies, it is still possible to verify the correct solution. Or at least, what's in the safe isn't the
solution per say.
As for the unsolvability of it, it's not only due to the
sample size but also to do with
intentional errors in the process. The algorithm used is actually fairly well known (polyalphabetic substitution). The issue lies in the fact that the originally encoded message contains spelling errors: the fourth panel doesn't conform to normal letter distributions (e.g. spelling "four" p-h-o-r or throwing a random Qs in)
Panel 4 remains a mystery due to the fact that it requires the other panels (as hints) to be solved and that there are more misspellings (complicating the process of deriving a correct solution) and less so in the guy's method of encoding the message.
Story on the subject.