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 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 website, known as GC-Wiki, when he was employed by Dell and assigned to NSA in 2012. Snowden made a calculated decision to move from Dell Inc to another NSA contractor, Booz Allen Hamilton, because he would have wide-ranging access to NSA data at the latter firm, one source with knowledge of the matter said. Sources familiar with unpublished material Snowden downloaded said it also contains information about the CIA - possibly including personnel names - as well as other U.S. spy agencies such as the National Reconnaissance Office and National Geospatial-Intelligence Agency, which operate U.S. image-producing satellites and analyze their data. Officials believe that the "doomsday" cache is stored and encrypted separately from any material that Snowden has provided to media outlets.
first the secret encrypted cache was the same as Wikilkeas and or Assange had and which over time went public by an act of stupidity-sabotage (your pick) by a disgruntled volunteer. There is off course still discussion if it is the real cache but no wonder but these are mindgames to keep everybody guessing. They both said that the cache would be published if something happens to them. Unless you have found all the different versions of the cache you would not risk this. Any operation is normally balanced against the risks of discovery and other risks that may have to be calculated.
if you have lost control over information, that information is compromised and if it is compromised (this means that it is not being published and no newspaper in the world will publish lists of secret agents) you have to consider it as lost and you have to take the necessary precautions to save as many agents involved as necessary (as was done in the wake of the first diplomatic cables that were published by Wikileaks and embassies started sending people home or giving a visa for the US or for a friendly country and maybe a new identity).
it means that depending on the risks all agencies are now in the process of giving new identities to people that are on the documents that are lost but not yet published.
It also means that if the documents are encrypted the NSA can calculate how long it will take for others to break the encryption and how much time but that leaves out the fact that whoever has found the encrypted cache will throw whatever he can have at it because if there is one cache that you would want to sell or give to your or other authorities than it will be this cache (it can even be handed back to the NSA for x millions - and nobody would complain I think)
just an idea, how do they do this in Belgium, giving a new identity to an agent or operator because this is not that simple because to do it effectively the person has to die or disappear and the new person have to be credible enough (and not necessarily based upon a dead person of which people know that he is dead because we are living in the 21th century, you can look up those things now). It is off course easier to give each ageint several fake identities (and not place them on your intranet) and hand them out as needed. THis would be even more easy if there would be European cooperation.