The passage mainly discusses ___________.

Which of these does the author provide in the passage?

Based on the author’s opinion, it can be concluded that ciphers are (a)   .

What is the correct order in which a cipher is used?

According to the author, all of Kerchoff’s rules are impossible to follow in evolving a cipher.

Imagine you are a soldier who has captured an enemy soldier. You believe that the captured person is a messenger who carries a cipher. Send a note to your commanding officer describing the messenger and the cipher.

According to the passage, a good cipher must take a (a)   time for the enemy to decipher, but at the same time, it must also be (b)   for the person sending the message to encipher it.

Which set of words from the passage can be considered antonyms?

All radio messages sent out can be copied athostilestations within radio range.The underlined word is similar in meaning to (a)   .