Edward Snowden hopes his leaks of secret documents will lead to greater governmental transparency, he said in rare comments.
The fugitive former US national security contractor spoke to Time magazine after he was named runner-up behind the pope for its Person of the Year.
He told the magazine he chose to defy his obligations when he learned the scope of surveillance programmes conducted without being disclosed.
"What we recoil most strongly against is not that such surveillance can theoretically occur, but that it was done without a majority of society even being aware it was possible," he said in an e-mail interview.
Snowden, who is living in Russia under temporary asylum and was branded "the dark prophet" by Time, has given few interviews since leaking a trove of secret documents from the US National Security Agency (NSA).
He said he decided to take the risk because of the dangers he saw of a surveillance state.
"The NSA is surely not the (East German) Stasi, but we should always remember that the danger to societies from security services is not that they will spontaneously decide to embrace moustache twirling and jackboots to bear us bodily into dark places, but that the slowly shifting foundation of policy will make it such that moustaches and jackboots are discovered to prove an operational advantage toward a necessary purpose," he told Time.
He hoped his disclosures would help bring about changes by forcing a rethink by the public, the technology community, the US courts, Congress and the executive branch.
Snowden was given asylum in Russia in August, angering the United States, where he could face espionage charges.
Time said Snowden was settling into his new life in Russia and was learning the language.