If you're a brilliant mathematician who has made a breakthrough in breaking cryptography, wouldn't you want to make a deal with the NSA? Reveal breakthrough in return for more knowledge.
That is, if I wanted to make any kind of deal with the NSA.
It might just be easier for them to say "Thanks, but we already knew that, and by the way that's ultra classified so we'll give you the option of a clean suicide."
1) Publish. Get famous. Guaranteed employment for the rest of your life.
2) Use it to break into systems. Become rich or get caught and jailed, likely for life.