Questions H3

Name:

Homework 3

Question 1 [7 pts]

Describe how a block cipher works by drawing a simple diagram showing all the components of the operation.

Question 2 [7 pts]

What is the codebook attack? Why this attack is feasible when 16 or 32-bit blocks have been used; but not feasible when 64-bit blocks have been used?

Question 3 [7 pts]

Describe two methods for constructing block ciphers. What is a round in block ciphers? How a slide attack is realized?

Question 4 [7 pts]

Compare EBC and CBC modes of operations? Why one should not use EBC? How the plaintext messages whose length is not a multiple of the block length is encrypted by using CBC?

Question 5 [7 pts]

Explain the Padding Oracle Attack.