AP CSP #52-56

In public key cryptography, the sender uses the recipient’s public key to encrypt a message. Which of the following is needed to decrypt the message?

• The sender’s public key

• The sender’s private key

• The recipient’s public key

• The recipient’s private key

In a certain science experiment, 75 percent of trials are expected to be successful and 25 percent of trials are expected to be unsuccessful. The program below is intended to simulate the results of repeated trials of the experiment.

Which of the following can be used to replace <MISSING CODE> so that the simulation works as intended?

• RANDOM (1, 100) = 25

• RANDOM (1, 100) ≤ 25

• RANDOM (1, 100) = 75

• RANDOM (1, 100) ≤ 75

The code segment below is intended to display all multiples of 5 between the values start and end, inclusive. For example, if start has the value 35 and end has the value 50, the code segment should display the values 35, 40, 45, and 50. Assume that start and end are multiples of 5 and that start is less than end.

Which of the following could replace <MISSING EXPRESSION> in line 2 so that the code segment works as

intended?

• end - start + 1

• end - start + 6

• ((end - start) / 5) + 1

• 5 * (end - start) + 1

The procedure below searches for the value target in list. It returns true if target is found and returns false otherwise.

Which of the following are true statements about the procedure?

I. It implements a binary search.

II. It implements a linear search.

III. It only works as intended when list is sorted.

• I only

• II only

• I and II

• II and III

Which of the following is an example of symmetric encryption?

• Evy buys a locked box that operates using two different codes. When the first code is entered, a slot opens that allows a message to be put in the box. When the second code is entered, the door to the box opens. Evy gives the first code to her friends so they can leave messages for her and keeps the second code to herself so that she is the only one who can retrieve the messages.

• Finn and Gwen develop a system that maps each letter of the alphabet to a unique symbol using a secret key. Finn uses the key to write a message to Gwen where each letter is replaced with the corresponding symbol. Gwen uses the key to map each symbol back to the original letter.

• Hannah writes a message to send to Isabel and hides the message under a rock behind the soccer field.

  Hannah gives Isabel the exact location of the rock so that only Isabel can find the message.

• Juan writes a message to send to Kelly and slides the message through a slot in the front of Kelly’s locker.

  Juan knows that Kelly has not shared her locker combination with anyone, so no one other than Kelly will

  be able to read the message.