The whistleblower Edward Snowden has declared “mission accomplished”, seven months after revelations were first published from his mass leak of National Security Agency documents.

The documents, which were passed to the Guardian, as well the Washington Post and other publications, revealed how technological developments were used by the US surveillance agency to spy on its own citizens and others abroad, and also to spy on allies, such as the US on Germany and Australia on Indonesia.

In 14 hours of interviews with Washington Post journalist Barton Gellman, Snowden said: “For me, in terms of personal satisfaction, the mission’s already accomplished.”

He continued: “I already won. As soon as the journalists were able to work, everything that I had been trying to do was validated. Because, remember, I didn’t want to change society. I wanted to give society a chance to determine if it should change itself.

“All I wanted was for the public to be able to have a say in how they are governed.”

Snowden said other colleagues at the NSA had been concerned the agency was spying on “more Americans in America than Russians in Russia” and were not entirely comfortable with the data collected on “ordinary” citizens.

He described using the “front-page test” on his colleagues when raising the issues, asking them how they thought the public would react if information was reported on the front page of a newspaper.

He said he had brought his concerns to at least four superiors and 15 colleagues at the NSA and used a heatmap from the data query tool BOUNDLESSINFORMANT to show how much data the agency was collecting.

The NSA told the Washington Post that none of these approaches had taken place.

Snowden also said he had suggested changing NSA systems so there would need to be a second authorisation for copying files to a hard drive but was rejected.

If his suggestion had been implemented Snowden would not have been able to copy all the files he took. An NSA spokeswoman also denied those conversations had taken place.

“I am not trying to bring down the NSA, I am working to improve the NSA,” Snowden said.

“I am still working for the NSA right now. They are the only ones who don’t realise it.”

Snowden revealed a little of his life in asylum in Moscow. He likened himself to an ascetic and a house cat and said he rarely left the house, spending most of his days surfing the internet – though visitors have brought him piles of books.

He does not drink – he says he never has – and lives mostly on ramen noodles.

There has been speculation that Snowden has rigged up a type of “dead man’s switch” so if the NSA, or a similar spy agency, hurt or kill him, then a cache of thousands of documents would be released on to the internet.

Snowden denied this and likened the scenario to a “suicide switch”, alluding to people who might want the information on the internet, unchecked and unredacted, and would kill him for the sake of it.

He named the chairs of the Senate and house intelligence committee, Dianne Feinstein and Mike Rogers, as people who had “elected” him to his whistleblower position by not doing their jobs properly in ensuring the oversight of the NSA.

“It wasn’t that they put it on me as an individual – that I’m uniquely qualified, an angel descending from the heavens – as that they put it on someone, somewhere,” he said.

“You have the capability, and you realise every other [person] sitting around the table has the same capability but they don’t do it. So somebody has to be the first.”

He said he had no relationship with the Russian government. “If I defected at all, I defected from the government to the public,” he said.