Originally posted on Turing's Invisible Hand:
The National Security Agency (NSA) has recently declassified an amazing letter that John Nash sent to it in 1955. It seems that around the year 1950 Nash tried to interest some US security organs (the NSA itself was only formally formed only in 1952) in an encryption machine of his design, but they did not seem to be interested. It is not clear whether some of his material was lost, whether they ignored him as a theoretical professor, or — who knows — used some of his stuff but did not tell him. In this hand-written letter sent by John Nash to the NSA in 1955, he tries to give a higher-level point of view supporting his design:
In this letter I make some remarks on a general principle relevant to enciphering in general and to my machine in particular.
He tries to make sure that he will be taken seriously: