Portside

Edward Snowden, the NSA whistleblower whose unprecedented leak of top-secret documents led to a worldwide debate about the nature of surveillance, insisted on Monday that his actions had improved the national security of the United States rather than undermined it, and declared that he would do it all again despite the personal sacrifices he had endured.

In remarks to the SXSW culture and technology conference in Texas, delivered by video link from his exile in Russia, Snowden took issue with claims by senior officials that he had placed the US in danger. He also rejected as demonstrably false the suggestions by some members of Congress that his files had found their way into the hands of the intelligence agencies of China or Russia.

Snowden spoke against the backdrop of an image of the US constitution, which he said he had taken an oath to protect but had seen “violated on a mass scale” while working for the US government. He accepted praise from Sir Tim Berners-Lee, the inventor of the world wide web, accorded the first question via Twitter, who described him as “acting profoundly in the public interest”.

The session provided a rare and extensive glimpse into the thoughts of Snowden, granted temporary asylum by Russia after the US revoked his passport. He struck back strongly against claims made again last week by the NSA director, General Keith Alexander, that his release of secret documents to the Guardian and other outlets last year had weakened American cyber-defences.

“These things are improving national security, these are improving the communications not just of Americans, but everyone in the world,” Snowden said. “Because we rely on the same standard, we rely on the ability to trust our communications, and without that, we don’t have anything.”

He added later that thanks to the more secure communication activity that had been encouraged by his disclosures, “the public has benefited, the government has benefited, and every society in the world has benefited”.

Snowden rejected claims that potential adversaries of the US, such as Russia and China, had obtained the files he had been carrying. “That has never happened, and it is never going to happen. If suddenly the Chinese government knew everything the NSA was doing, we would notice the difference,” said Snowden, noting that US infiltration of Russia and China was extensive.

He sharply criticised Alexander and Michael Hayden, his predecessor as NSA director, as the two officials to have most “harmed our internet security and actually our national security” in the era since the September 11 terrorist attacks by “elevating offensive operations” over cyber-defence.

“When you are the one country in the world that has a vault that is more full than everyone else’s, it doesn’t make any sense to be attacking all day and never defending your vault,” he said.

“And it makes even less sense when you let the standards for vaults worldwide have a big back door that anyone can walk in.”

The 30-year-old also claimed that by spending so much effort on harvesting communications data en masse, US security agencies were failing to pick up would-be terrorists such as Tamerlan Tsarnaev, one of the brothers alleged to have bombed last year’s Boston Marathon, who had been previously flagged to the US as a cause for concern by Russian authorities. “We are monitoring everyone’s communications rather than suspects’ communications,” he said. “If we hadn’t spent so much on mass surveillance, if we had followed traditional patterns, we might have caught him.”

Snowden also pointed to the case of Umar Farouk Abdulmutallab, the so-called “underwear bomber” who attempted to blow up a plane bound for Detroit on Christmas Day 2009. The US failed to intercept him despite several opportunities, including a warning from his father to US officials in Nigeria.

An audience of 3,500 packed into an auditorium in Austin applauded several of Snowden’s answers to questions from a pair of onstage moderators and others submitted through Twitter. Despite a glitchy and intermittent video link that he said was running through seven proxies, Snowden looked relaxed and confident.

He said that while the US has “an oversight model that could work” to guard against excess by intelligence agencies, in reality it had proved ineffectual. “The problem is when your overseers are not interested in oversight,” he said, and “champion the NSA instead of holding them to account”.

James Clapper, the director of national intelligence, has admitted to not telling the truth when he told a congressional hearing last year that the government was not “collecting data on millions of Americans”. Snowden said Clapper had shown officials “can lie to the country, lie to the Congress, and face not even a criticism”.

He claimed that the behaviour of the US in online surveillance policy would only encourage the rest of the world to do the same, endangering the privacy of all citizens. “If we don’t resolve these issues, if we allow the NSA to continue unrestrained, every other government will accept that as a green light to continue, and that is not what we want,” he said.

Snowden stressed that his message to technology firms such as Facebook and Google was “not that you can’t collect any data” but rather “that you should only collect the data, and hold it as long is necessary, for the operation of your business”.

He recently became the victim of a hacking when a scan of his US passport was released online, having been taken from the files of a professional organisation that gives certification to “ethical” hackers. “I submitted those forms back in 2010,” said Snowden. “Why was that still on a web-facing terminal?”

He encouraged ordinary internet users to protect themselves against surveillance by encrypting both their hard drives and their online activity, describing encryption as “the defence against the dark arts in the digital realm”. He also advised people to browse the web anonymously using the Tor system.

He urged software developers to create more user-friendly secure communications tools that could “pass the Glenn Greenwald test”, referring to Greenwald’s inability to communicate securely using PGP encryption when he first approached the journalist, then working for the Guardian. However, he warned: “If you are a target of the NSA, it is game over no matter what unless you are taking really technical steps to protect yourself.”

Despite now being unable to return to the US, where he faces a criminal indictment, a defiant Snowden said he did not regret his decision to orchestrate the biggest leak in the history of US intelligence. “Would I do this again? The answer is absolutely yes,” he said. “Regardless of what happens to me, this is something we had a right to know.”

By the end end of his interview, the audience was on its feet to deliver a standing ovation. Snowden smiled and looked slightly embarrassed, before being abruptly cut off by the end of the video call, when the screen fell blank.