In January 2013, film-maker Laura Poitras received an encrypted e-mail from a stranger who called himself Citizen Four. In it, he offered her inside information about illegal wiretapping practices of the NSA and other intelligence agencies. Poitras had already been working for several years on a film about mass surveillance programs in the United States, and so in June 2013, she went to Hong Kong with her camera for the first meeting with the stranger, who identified himself as Edward Snowden. She was met there by investigative journalist Glenn Greenwald and The Guardian intelligence reporter Ewen MacAskill. Several other meetings followed. Citizenfour is based on the recordings from these meetings. What follows is the largest confirmations of mass surveillance using official documents themselves, the world has never seen…