From an interview in Vogue, of all places, which really says a lot about how widely this story has permeated popular culture:
"The first email came in January 2013. And that was a very simple email—just basically saying, "I'd like to get your encryption key. Your public key," which I sent back. The next response was the one that you see at the beginning of the film where he says, "I'm a member of the intelligence community and this won't be a waste of your time."