Surveillance whistleblower Edward Snowden has told a Dublin audience he would still like to live in Ireland.

The former US Central Intelligence Agency computer specialist, whose revelations about a vast and unauthorised global surveillance programme by America’s National Security Agency led to his exile in Russia, was on video link from his Moscow apartment.

He was en route to Latin America in 2013 when the US froze his passport, trapping him in Moscow. He appealed to many countries to grant him asylum, including Ireland.

Asked at the Cyber Threat Summit 2017 in DCU’s Helix if he would still like to live in Ireland, he replied: “Of course! I asked for it once!”

But in reality, it would take political will for that to happen, he said. “We can have the support of every member of the public in Ireland but if the Irish government isn’t rowing back, nothing’s changed,” he said.

The 34-year-old, reviled by those who say he betrayed the secrets that keep the West safe but admired by others who believe governments should be accountable and held in check, appeared relaxed and was, in turn, serious and cheerful but deadly earnest about his mission.

In 2012 and 2013, Snowden worked with the Guardian, the Washington Post and Wikileaks to publish thousands of NSA documents. They showed the US was spying on ordinary citizens on an epic, previously unknown and unauthorised scale.

He had no regrets, he told his largely admiring and supportive audience, and sought to justify his action. The US government granted itself “powers the people never granted because they know it is better to ask forgiveness than permission,” he said.

“There should be no surveillance that’s occurring today that is happening in bulk,” he said in answer to questions by conference organiser Paul Dwyer.

“Traditionally, surveillance had always been a targeting problem, or a selection problem. The police go, ‘we think this person or that person is a criminal, they’re up to no good, they’re a terrorist’.

“They go to court, they show their evidence for thinking this to the judge and the judge says this is reasonable and they authorise them to begin spying as much as they want on this particular person.”

The technology that was being used was changing surveillance from a problem of selecting targets into a ranking problem in which everyone was assessed. As a result, he said, “we are all on the list, it’s just a question [of] how high up you are”.

Mr Snowden urged his audience to question all powerful institutions and seats of authority.

Threats of terrorism, used by politicians to justify invasions of privacy, were illusory, he suggested. The number of people dying in terrorism-related incidents was greater in the 1960s than today, despite recent outrages in Europe.

“People like to think of the law as establishing how governments work but the law only has that effect insofar as the government abides by the law,” he said. “When I came forward, the reason it has so much impact around the world was because the government was violating the laws in the United States. The UK was violating its laws. And this was why they all tried to rush through to legalise what they were doing.”

He described his life in Moscow as “pretty ordinary” and said he would prefer to be at home.

“As a dissident, I think it is absolutely tragic, even repulsive, that the only place an American whistleblower can be safe is in Russia. I think Europe would agree that this is not an ideal situation,” he said.

“And this is why of course, I would still love to go home, and I told the US I have only a single condition for going back, actually volunteering myself for a trial, which certainly won’t be fair, and that is to be allowed make a public interest defence – that I can tell the truth why it is I did what I did. And they said they won’t agree to that but they promise not to torture me.”

He said his “ultimate message” was about what people could do to make the world a better place and that could only be done through “collective action”.

“But that collective action starts with individual choices – looking around at the world you live in, the things that you see around us and recognising that we all have minds of incivility, of injustice, that we can except and we can deal with.

“We can see the homeless, the panhandler and go, not today, I can’t handle it. But then you see it again and then you see it again and then eventually you feel, you’re going to do something.

“There’s that one step beyond where you can no longer countenance being a part of that and that is when you recognise that you have not just the right but the duty and obligation to make this world better in whatever ways we can.”