Amnesty for Edward Snowden? Might depend on what secrets he's got left.

The question of whether Edward Snowden might one day win amnesty in the US or political asylum elsewhere may hang largely on whether a reported cache of 1.5 million still-unreleased top-secret documents exists and remains under wraps.

Nobody, not apparently even the National Security Agency, knows how many top-secret documents the former NSA contractor copied into his own encrypted archives. But an NSA official on CBS’s “60 Minutes” on Sunday would not deny that Snowden may have taken as many as 1.7 million documents.

If Snowden has released to the press between 50,000 and 200,000 documents, as NSA chief Gen. Keith Alexander said in October, that leaves some 1.5 million documents unaccounted for. More significantly, those documents are likely to be much more harmful to American security interests than what has been released so far, several cyber espionage experts say.

That means US officials might be more willing to consider amnesty – or other nations might be open to Mr. Snowden’s pleas for asylum – if they can get their hands on Snowden’s remaining stash.

“Most of the revelations of Snowden so far are programs that foreign governments knew or suspected we were doing, so these revelations don’t do much more than confirm their suspicions,” says a former senior NSA official speaking on condition of anonymity in order to maintain good relations with former colleagues at the agency. “But some specific revelations, if they surfaced from remaining documents, could embarrass people into shutting down relationships with the NSA. It would have an adverse operational impact.”

On “60 Minutes,” Richard Ledgett, who is under consideration to become the agency’s top civilian, said he’d at least consider amnesty for the return of the remaining documents if he could be convinced that the documents have not been released of perused by a third party.

“My personal view is, yes, it’s worth having a conversation about,” Mr. Ledgett said, acknowledging that his bar “would be very high.”

For its part, the Obama administration      has disavowed the amnesty idea. Snowden “faces felony charges here, he ought to be returned to the United States, again, where he will face full due process and protection under our system of justice, that we hope he will avail himself of,” White House spokesman Jay Carney told reporters Monday.

But if Snowden has more than a million additional documents, they could be of crucial importance to US intelligence operations.

For instance, one of the documents leaked by Snowden highlighted Xkeyscore, an NSA program that allows the agency to sift through the haystack of digital global communications to find the needle of terrorist activity. One particular document reported by The Washington Post and the Guardian in late July showed a world map with red dots denoting Xkeyscore nodes or collection points.

What was not revealed were specifics about those collection points.

“Most of the red dots in the Xkeyscore map are probably countries that are cooperating with the US and the NSA,” says James Bamford, an author who has spent most of his life investigating the NSA and written several books. “But some may be covert operations where US has bribed someone to get bugged equipment into that location – or the agency is tapping into it in a different way.”

Indeed, the dots on the map indicate some international locations “where the US wouldn’t logically have any cooperative agreements, including countries like Brazil and Argentina,” Mr. Bamford notes. “Some dots may represent locations where they subverted workers at a telecommunications or other facilities.”

The remaining trove of documents could also detail specific sources and methods of code-breaking in potentially hostile nations.

“With all that’s been released so far about NSA activity in the US, there really hasn’t been anything related to North Korea or Iran, Russia, “ Bamford says. “This is what really worries the NSA – having documents released that show specifically how we’re doing our spying on those countries.”

Snowden has maintained that his primary intent has been to reveal mass surveillance directed at Americans and other Western democracies by the NSA, not to help America’s adversaries.

But if that’s true, he might find it hard to publish the rest of his potential trove. He could release documents to media operations unlikely to reveal “sources and methods” indiscriminately. Or he could just sit on the remaining pile.

Complicating matters is the question of how much of the trove Snowden still controls exclusively. How much do journalists Glen Greenwald and Laura Poitras have? How secure is the rest, given that he’s almost certainly under tight surveillance in Russia, where he has been granted temporary asylum?

“The Russian FSB [intelligence agency] doubtless has him completely under their control,” says James Lewis, a cyber conflict expert at the Center for Strategic and International Studies in Washington. “If he tries to type in a password into a computer in his room, they will intercept it.”

Whether the US eventually negotiates over the unreleased documents may depend on what officials think he has. If they think his documents imperil the many billions of dollars the NSA has spent during the past decade to develop its global surveillance networks, that could be a strong incentive to play ball.

“We might have seen the political effect of these document leaks peak, while the operational effect might not have done so just yet,” Mr. Lewis says. Ledgett’s comment “about amnesty might have been an effort to find out what he actually has left. It’s a way of telling Snowden, “OK, it’s your turn. You have to bid.”

One thing is clear, the Obama administration has been the toughest administration in history when it comes to going after national security leaks using the Espionage Act, which can result in life in prison.

The White House’s options might also shift if Snowden gets into a bidding war. Snowden has been soliciting offers for permanent asylum. Earlier this year, he appealed to Germany, saying he would like to testify before parliament there, but couldn’t so as long as he was threatened with arrest. On Monday, he published an open letter to Brazil in the Guardian.

Documents Snowden released this fall show that Brazil was a top NSA target in Latin America. The agency was monitoring Brazilian President Dilma Rousseff’s cellphone, as well as Petrobras, the national oil company.

In a letter released Tuesday, Snowden offered to help Brazil investigate NSA spying against it but needed political asylum, because the US “government will continue to interfere with my ability to speak.”