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

People are starting to understand that the devices we carry with us reveal our location, who we're talking to, and all kinds of other information.

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.

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.

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.

Snowden is almost preternaturally prepossessing and self-possessed. I think of a novelist whose dream character just walks into his or her head. It must have been like that with you and Snowden. But what if he'd been a graying guy with the same documents and far less intelligent things to say about them? In other words, how exactly did who he was make your movie and remake our world?

One of the things that I think is true is that encryption actually is able to secure our communications, that every individual can use encryption, and that it's accessible and in many cases free.