In all my work, I'm interested in understanding big issues through the lives of individuals.

We've already seen shifts happening in some of the big companies - Google, Apple - that now understand how vulnerable their customer data is, and that if it's vulnerable, then their business is, too, and so you see a beefing up of encryption technologies. At the same time, no programs have been dismantled at the governmental level, despite international pressure.

When the most important decisions are made in secret, we lose our ability to check the powers that control.

It's not everyday that a whistleblower is actually willing to be identified.

I think one of the most shocking things is how little our elected officials knew about what the NSA was doing. Congress is learning from the reporting and that's staggering. Snowden and [former NSA employee] William Binney, who's also in the film as a whistleblower from a different generation, are technical people who understand the dangers.

That's a question you'd have to present to people in the White House.

One of the most frightening things, I think, is the capacity for retroactive searching, so you can go back in time and trace who someone is in contact with and where they've been.