British and US intelligence officials say they are worried about a “doomsday” cache of highly classified, heavily encrypted material they believe former National Security Agency (NSA) contractor Edward Snowden has stored on a data cloud.
The cache contains documents generated by the NSA and other agencies and includes the names of US and allied intelligence personnel, seven current and former US officials and others, sources briefed on the matter said.
The information is protected with sophisticated encryption and multiple passwords are needed to open it, said two of the sources, who, like the others, spoke on condition of anonymity.
The passwords are in the possession of at least three different people and are valid for only a brief time window each day, they said. The identities of people who might have the passwords are unknown.
Spokespeople for both the NSA and the US Office of the Director of National Intelligence declined to comment.
One source described the cache of still unpublished material as Snowden’s “insurance policy” against arrest or physical harm.
US officials and other sources said only a small proportion of the classified material Snowden downloaded during stints as a contract systems administrator for the NSA has been made public. Some officials in the administration of US President Barack Obama have said privately that Snowden downloaded enough material to fuel two more years of news stories.
“The worst is yet to come,” said one former US official who follows the investigation closely.
Snowden, who is believed to have downloaded between 50,000 and 200,000 classified NSA and British government documents, is living under temporary asylum in Russia, where he fled after traveling to Hong Kong. He has been charged in the US under the Espionage Act.
Cryptome, a Web site which started publishing leaked secret documents years before WikiLeaks or Snowden surfaced, estimated that the total number of Snowden documents made public so far is more than 500.
Given Snowden’s presence in Moscow and the low likelihood that he will return to the US anytime soon, US and British authorities say they are focused more on dealing with the consequences of the material he has released than trying to apprehend him.
It is unclear whether US or allied intelligence agencies — or those of adversary services, such as Russia’s and China’s — know where the material is stored and, if so, have tried to unlock it.
One former senior US official said that the Chinese and Russians have cryptographers skilled enough to open the cache if they find it.
Snowden’s revelations of government secrets have brought to light extensive and previously unknown surveillance of telephone, e-mail and social media communications by the NSA and allied agencies. That has sparked several diplomatic rows between Washington and its allies, along with civil liberties debates in Europe, the US and elsewhere.
Among the material which Snowden acquired from classified government computer servers, but which has not been published by media outlets known to have had access to it, are documents containing names and resumes of employees working for the NSA’s British counterpart, the Government Communications Headquarters (GCHQ), sources familiar with the matter said.
The sources said Snowden started downloading some of it from a classified GCHQ Web site, known as GC-Wiki, when he was employed by Dell and assigned to the NSA last year.