A short while ago, the National Geographic Channel aired a one hour special on the NSA, the first time cameras had been allowed into the facility since 9/11. At the end of the program, historians at the NSA's Cryptologic Museum declassified 60 year old letters from John Nash to the agency. Average people will recognize that name as the subject of A Beautiful Mind". The letters themselves (show some horrendous handwriting) go into detail about cipher systems based on computational complexity as the key to future cryptography. His theories essentially predate most published concepts on such cryptographic systems by nearly two decades.