2-33. A command post bunker switchboard received a request for illumination at Concentration
35. A patrol was operating in that vicinity, and the illumination was provided. A few minutes
later a request was received for high explosive artillery fire at Concentration 1 which, on the
alternate defense plan, was the same as Concentration 35. This request was followed by an
instant "out." Authentication, therefore, could not be initiated, but the patrol was called
immediately for verification. It was found that the patrol, well within the perimeters of
Concentrations 1 and 35, had not requested either the high-explosive fire or the illumination.
There are many instances when ______________________ is not mandatory, but it is desirable
when making initial contact or resuming contact after prolonged interruptions. When initial
contact is made, or contact is resumed after prolonged interruptions, _____________ is
(2-33. Answer: authentication, authentication)
2-34. Authentication is mandatory when a station is authorized to transmit a classified message
in the clear and when transmitting in the blind; that is, without getting a receipt for its traffic.
The station authorized to transmit a classified message in the _____________ must
_____________. A station transmitting in the _____________ must _____________.
(2-34. Answer: clear, authenticate, blind, authenticate)
2-35. A test element and an authenticator are used in the _____________and _____________
authentication system. In the transmission authentication system, _____________ are used.
(2-35. Answer: challenge, reply, digraphs)
2-36. The transmission authentication table consists of numbered columns of _____________.
The challenge and reply authentication table consists of columns of _____________.
(2-36. Answer: digraphs, letters)