🚀 go-pugleaf

I was reading a recent Clancy-style novel and it was describing
an AWACS controlled fighter battle. In it, the use of IFF
was described. IFF (Identify Friend or Foe) is used by both
civilian and military aircraft. In the civilian case, a
an interrogator associated with a radar sends out a signal,
and the IFF transponder replies with information coded
to show the "squalk code" and, in mode C, the altitute.

My question is: how does the military system work. It has
the following additional requirements:
  (1) It should only respond to a "friendly" interrogator
  (2) It should not emit easily detectable signals
  (3) It's signals should be encrypted so that, if they are intercepted,
      they provide minimal information to the enemy.

Does anyone know how this is done and how many of the above
requirements are met?
-- 
John Moore (NJ7E)           mcdphx!anasaz!john asuvax!anasaz!john
(602) 861-7607 (day or eve) long palladium, short petroleum
7525 Clearwater Pkwy, Scottsdale, AZ 85253
The 2nd amendment is about military weapons, NOT JUST hunting weapons!