Kryptos - Sculpture at the CIA headquarters that continues to be of interest to cryptanalysts for its fourth passage that has yet to be deciphered

Still??? I heard about this in college when I tried computer science out. Wow!

Probably a one time pad, and thus cant ever be solved.

NPR has done stories about this in the past:

https://www.npr.org/2010/11/22/131520768/-kryptos-sculptor-drops-new-clue-in-20-year-mystery