•	U-2
•	SR-71
•	Corona
•	Minox camera
•	Microdots
•	Bugs
•	Invisible ink
•	Bug detectors
•	TEMPEST
•	Hidden still cameras
•	Hidden video cameras
•	Hidden audio recorders
•	Fiberscope
•	One-time pad
•	Cray Supercomputer
•	Infrared telephone
•	Invisible ink
•	Dead-drop spike
•	Hollow coin concealment
•	Dead-drop bolt