Part of the problem isn't over whether information is encrypted or not. It relates to the number of people with the highest-level of security clearance in the USA.
It would be easy to think that only the President, his Chiefs of Staff, other very senior military personnel, some very senior diplomats & civil servants and a few others might have such clearance. However there are actually around 854,000 Americans who've got top-level security clearance. So, if only 1 person in every eighty five thousand would be prepared to leak information, that still provides 10 sources of leaks.
Chris