(d) The requirement is to identify a method of reducing
security exposure when transmitting proprietary data over communication
lines. Answer (d) is correct because cryptographic
devices protect data in transmission over communication lines.
Answer (a) is incorrect because asynchronous modems handle
data streams from peripheral devices to a central processor. Answer
(b) is incorrect because authentication techniques confirm
that valid users have access to the system. Answer (c) is incorrect
because call-back procedures are used to ensure incoming calls
are from authorized locations.