Edward Snowden spoke to a crowd at the South By Southwest (SXSW) conference in Austin through "seven proxies" in order to prevent circumvention or disruption of the feed by US intelligence services.
He spoke out against the systems of mass surveillance carried out by the American National Security Agency (NSA) and the UK's own Government Communications Headquarters (GCHQ), describing them as "setting fire to the future of the Internet".
The keynote went ahead despite one Kansas lawmaker asking SXSW organisers to cancel the video chat session, arguing that the conference should not give the former NSA contractor a platform.
Snowden argued that as well as attacking mass surveillance through legal challenges, technology companies could single-handedly make the kind of mass surveillance seen in programmes such as PRISM and XKeyscore prohibitively expensive.
"The primary challenge for mass surveillance for any government in the world isn't just how do you collect all the information travelling through the networks, but how do you analyse it – how do you get the important information out?"
He argued that if tech companies took encryption seriously, this would have a knock-on effect on the accountability of surveillance agencies.
"By doing end-to-end encryption, you force surveillance companies to go to the endpoints – and what you get from that is a more enforceable, a more accountable type of surveillance. You have to target the surveillance at individuals, rather than pitching surveillance at everyone in the world."
The conversation was carried out over Google Hangouts, the irony of which the hosts said was not lost on them.
"America has more to lose in these cyber attacks," Snowden said.
"When characters like General Keith Alexander say that these leaks have damaged American national security, it doesn't make sense. If we have backdoors encoded into the Internet that anyone can just walk into, we're less secure."
When asked if the NSA's surveillance techniques were effective, Snowden didn't hesitate.
"They're not," he said.
"The reality is that when they did it, they found out it didn't work. But [the programme] was so successful in gaining funding, in getting support, that nobody wanted to say it. Two independent White House investigations have said that it has no value it all, it hasn't helped us."
He accused the disproportional focus on signals intelligence for failings that led to the Boston Marathon bombings last April.
"The lack of focus has led to us being less informed. If we hadn't spent so much on this surveillance, we might have caught them," he said.
"Encryption does work," he said. "We need to stop thinking of it as some arcane dark art, but simply part of our basic protection."