Question 10

1. Given a 2-digit PIN with each digit taking a value from 0-9 (10 choices for each digit), it takes 20 seconds on average to compromise such a PIN if the attack rate is 5 password attempts per second.

   True

   False

1 points

Question 11

1. The major use of symmetric encryption is to achieve confidentiality and integrity.

   True

   False

1 points

Question 12

1. Generating a message authentication code (MAC) requires a secret key, and the message sender and receiver hold different such keys.

   True

   False

1 points

Question 13

1. In block cipher, the length of ciphertext and the length of plaintext can be different.

   True

   False

1 points

Question 14

1. Secure hash functions (e.g., SHA-1) cannot be used for message authentication because there is no input of a secret key to the hash function.

   True

   False

1 points

Question 15

1. CBC and CTR are two modes of operations with a chaining structure, i.e., message blocks are connected sequentially.

   True

   False