QUESTION 1

1. Match each security term to the corresponding definition. [10 Marks]

   - A. B. C. D. E. F. G. H. I. J.	Plain Text
   - A. B. C. D. E. F. G. H. I. J.	Cipher Text
   - A. B. C. D. E. F. G. H. I. J.	Key
   - A. B. C. D. E. F. G. H. I. J.	Encryption
   - A. B. C. D. E. F. G. H. I. J.	Decryption
   - A. B. C. D. E. F. G. H. I. J.	Cryptography
   - A. B. C. D. E. F. G. H. I. J.	Cryptonalysis
   - A. B. C. D. E. F. G. H. I. J.	Confusion
   - A. B. C. D. E. F. G. H. I. J.	Diffusion
   - A. B. C. D. E. F. G. H. I. J.	Cryptology

   A.	A technique for hiding the relationship between a key and cipher text.
   B.	Hiding the relationship between plain text and cipher text.
   C.	Study of both how to protect messages using ciphers and how to break ciphers without knowledge of the cipher key.
   D.	Conversion of a message from plain text to cipher text
   E.	Original message
   F.	Study of principles on how to decrypt cipher text without knowing the key.
   G.	Study of encryption and decryption methods and principles
   H.	Encrypted message
   I.	Information used in a cipher that is kept confidential between the sender and receiver of a message
   J.	Recovery of the original message from a cipher text

10 points

QUESTION 2

1. For an AES-128 cipher, if K₇= E749039456217663674597F2D13C3A43₁₆, what would be the first word for K₈? [30 Marks]

30 points

QUESTION 3

1. In an AES-128 cipher, if the input to the SubBytes stage is E749039456217663674597F2D13C3A43₁₆, what is the output of the ShiftRows stage? [18 Marks]

18 points

QUESTION 4

1. Which of the following is a key similarity between a Feistel Network and the substitution permutation network? [2 Marks]

   		Encryption and Decryption is the same function for both of them
   		There are no known attacks so far that have compromised ciphers that use these networks
   		They both use sub-keys in reverse order for decryption
   		Both include expansion in their key scheduling

2 points

QUESTION 5

1. A Linear Feedback Shift Register is defined as follows:

   >> s = [E2],

   >> t = [6 4],

   >> seq = LFSR(s,t)

   What will be the state and output bit stream of the register after 4 clock cycles? [15 Marks]

15 points

QUESTION 6

1. In a DES S-Box substitution, if the input is 4597F2D13C3A₁₆, what will be the output? [25 Marks]