Snowden shows incredible care for computer and network security. Perhaps the most peculiar is his method of password security. To prevent onlookers from watching him type his password, he covers his head, keyboard, and screen with a blanket. 
Also, he is very careful to encrypt his sensitive communications. The movie includes a lot of detail about his use of security. In the opening scene, a message from Snowden to Laura, the movie’s producer, is read aloud.  He asked her to confirm that no one has ever had access to her private key and that it is protected by a strong password. Shortly after this scene, the film states that when an anonymous source (presumably Snowden) attempted to contact journalist Glenn Greenwald, they weren’t able to communicate as they could not establish a secure means of communication.
Snowden is known for using Lavabit, an email service which doesn’t store emails on its server. In this way, the government can’t get emails by requesting them from Lavabit, as they don’t have them. 
 “Citizenfour” (HBO Films, 2014)
 “Lavabit Explained” https://lavabit.com/explain-lavabit.html (Accessed 04/23/2017)