Which of the following characteristics does a one-time pad have if used
properly?

A.
The key has to be of greater length than the message to be encrypted.

B.
The key does not have to be random.

C.
It can be used more than once.

D.
It is unbreakable.

Explanation:
The correct answer is “It is unbreakable”. If the one-time-pad is used only once and
its corresponding key is truly random and does not have repeating
characters, it is unbreakable.
Answer “It can be used more than once” is incorrect because if used
properly, the one-time-pad should be used only once.
Answer “The key does not have to be random” is incorrect because the key should be random.
Answer “The key has to be of greater length than the message to be encrypted” is incorrect

because the key has to be of the same length as the message.