A zero-day exploit is a method of hacking a system. It's sort of a vulnerability that has an exploit written for it, sort of a key and a lock that go together to a given software package. It could be an internet web server. It could be Microsoft Office. It could be Adobe Reader or it could be Facebook.

In America, we collect more digital communications from America than we do from the Russians.

I know that fundamentally, changes to the fabric of the internet, and sort of our methods of communication, can enforce our rights.

Let's put it this way. The United States government has assembled a massive investigation team into me personally, into my work with the journalists, and they still have no idea what documents were provided to the journalist, what they have, what they don't have, because encryption works.

If I and other whistleblowers are sentenced to long years in prison without so much as a chance to explain our motivations to a jury, it will have a deeply chilling effect on future whistleblowers working as I did to expose government abuse and overreach. It will chill speech. It will corrode the quality of our democracy.

Look at the reactions of liberal governments to the surveillance revelations during the last years. In the United States, we've got this big debate, but we've got official paralysis - because they're the ones who had their hand caught most deeply in the cookie jar.

The bare bones tools for a cyber-attack are to identify a vulnerability in the system you want to gain access to or you want to subvert or you want to deny, destroy, or degrade, and then to exploit it, which means to send codes, deliver code to that system somehow and get that code to that vulnerability, to that crack in their wall, jam it in there, and then have it execute.