Arcana imperii

Arcana imperii is a Latin term relating to classified information linked with reasons of state in the Terran Republic. It refers to the highest level of secrecy in the Terran Government and the Terran Armed Forces, second only to damnatio memoriae, which implies that documentation was outright destroyed. Officially, arcana imperii refers to Absolute Class-9 Access. There are only a few thousand people across the Federation with such a high access level. They are are referred to colloquially as the arcanists. 
More broadly, arcana imperii has been used to describe the amalgamation of propaganda and deception used by the Terran state to achieve its goals, domestically and abroad. This is particularly applied to intelligence agencies and experimental research agencies.