Julian Assange has distributed an encrypted “insurance file” with a 256-digit key. I am not sure what algorithm it uses, but a key that long would be almost impossible to break via a random number attack.
In the 1990s, I worked on one of Al Gore’s data encryption schemes for spying on the public’s digital communications. The rumour in the encryption community was that NSA would not allow any algorithm to propagate which does not have a back door approach that is known to NSA.
So Assange may not be quite as well protected as he thinks he is. NSA may well be extracting the guts of the message right now.