AQA A Level Computer Science 2

What are the conditions required for a Vernam cipher to be 100% mathematically secure?

• The key is used only once, and then destroyed/

• The key is made up of truly random characters/

• The key must be made up of fewer characters than the plaintext message.

• Different keys must be used to encrypt and decrypt a message.

The letter m has an ascii code of 1101101. As part of a Vernam cipher, the key 0101001 is applied to that letter. What is the resulting ciphertext?

• 1000100

• 0111011

• 1100101

• 1101001

Which of these are advantages of vector graphics over bitmap graphics?

• Can be rescaled without distortion

• (Usually) a smaller file size

• Ideal for photographic images

• Each pixel can be modified individually

The bitmap image of the lemming is 6 pixels by 10 pixels. There are 16 available colours for each pixel. Calculate the file size of the image (not including any metadata) in bytes.

• 30

• 120

• 22.5

• 60

How many different combinations of bit patterns can be represented using ASCII?

• 127

• 128

• 255

• 256

The bit pattern 0110001 is sent with an even parity bit in the MSB position.

Which of these is the bit pattern receivedt?

• 00110001

• 10110001

• 01100011

• 01100010

Data is received that had been sent using majority voting. The received bit pattern is 100 000 011 111.

What bit pattern does the receiving device interpret this as?

• 0011

• 1010

• 0001

• 1001

10.Complete this sentence: .edu is a ……………………… level domain.

• A.Top

• B.2nd

• C.3rd

11.Complete this sentence: A domain name is ……………………… in structure.

• A.Linear

• B.Sequential

• C.Hierarchical

Internet registrars are important because they hold all records of all existing website names and the details of those domains that are available to purchase.

How many Internet registrars are there in the world?

• 5

• 10

• 15

• 20