Snowden told The Guardian that he lacked a high school diploma and enlisted in the U.S. Army until he was discharged because of an injury, and later worked as a security guard with the NSA.
He later went to work for the CIA as an information technology employee and by 2007 was stationed in Geneva, Switzerland, where he had access to classified documents.
During that time, he considered going public about the nation's secretive programs but told the newspaper he decided against it, because he did not want to put anyone in danger and he hoped Obama's election would curtail some of the clandestine programs.
He said he was disappointed that Obama did not rein in the surveillance programs.
"Much of what I saw in Geneva really disillusioned me about how my government functions and what its impact is in the world," he told The Guardian. "I realized that I was part of something that was doing far more harm than good."
Snowden left the CIA in 2009 to join a private contractor, and spent last four years at the NSA, as a contractor with consulting giant Booz Allen Hamilton and, before that, Dell.
The Guardian reported that Snowden was working in an NSA office in Hawaii when he copied the last of the documents he planned to disclose and told supervisors that he needed to be away for a few weeks to receive treatment for epilepsy.
A sign advertising Century 21 realtor Kerri Jo Heim sits on the grass outside the blue-and-white house where Snowden and his girlfriend lived in a quiet neighborhood in Waipahu, West Oahu.
Heim says the couple moved out on May 1, leaving nothing behind. She said last Wednesday police came by asking where they went, but she didn't know.
Snowden left for Hong Kong on May 20 and has remained there since, according to the newspaper. Snowden is quoted as saying he chose that city because "they have a spirited commitment to free speech and the right of political dissent", and because he believed it was among the spots on the globe that could and would resist the dictates of the U.S. government.
"I feel satisfied that this was all worth it. I have no regrets," Snowden told The Guardian, which said he asked to be identified after several days of interviews.
Iceland's International Modern Media Institute, a free press group, said it had yet to hear from Snowden directly. But in a statement the institute said it would do what it could to help the former intelligence worker find asylum and was already working to set up a meeting with Iceland's newly appointed interior minister.
Snowden could face decades in a U.S. jail for revealing classified information if he is successfully extradited from Hong Kong, said Mark Zaid, a national security lawyer who represents whistleblowers. Hong Kong had an extradition treaty with the United States that took force in 1998, according to the U.S. State Department website.
"If it's a straight leak of classified information, the government could subject him to a 10 or 20 year penalty for each count," with each document leaked considered a separate charge, Zaid said.
Hong Kong, though part of China, is partly autonomous and has a Western-style legal system that is a legacy from the territory's past as a British colony. A U.S.-Hong Kong extradition treaty has worked smoothly in the past. Hong Kong extradited three al-Qaeda suspects to the U.S. in 2003, for example.
But the treaty comes with important exceptions. Key provisions allow a request to be rejected if it is deemed to be politically motivated or that the suspect would not receive a fair trial. Beijing may also block an extradition from Hong Kong for national security reasons.
Snowden told the newspaper he believes the government could try to charge him with treason under the Espionage Act, but Zaid said that would require the government to prove he had intent to betray the United States, whereas he publicly made it clear he did this to spur debate.
The government could also make an argument that the NSA leaks have aided the enemy — as military prosecutors have claimed against Army Pvt. Bradley Manning, who faces life in prison under military law if convicted for releasing a trove of classified documents through Wikileaks.