1. For the cipher text 0000 0111 0011 1000 and Key 0110 1111 0110 1011, apply the Simplified AES to obtain the plaintext. The plain text is
a) 0110 1001 0111 0001
b) 0110 1111 0110 1011
c) 0010 1001 0110 1011
d) 1111 0101 0111 1111
Explanation: On applying the simplified AES we would obtain 0110 1111 0110 1011 as the plain text.
2. What is the block size in the Simplified AES algorithm?
a) 8 bits
b) 40 bits
c) 16 bits
d) 36 bits
Explanation: The block size for the AES algorithm is 16 bits.
3. What is the key size in the S-AES algorithm?
a) 16 bits
b) 32 bits
c) 24 bits
d) None of the mentioned
Explanation: The key size in the S-AES algorithm is 16 bits.
4. S-AES and S-DES were both developed by the same person as an educational cryptography system to teach students
a) True
b) False
Explanation: True
5. Which of the following is a faulty S-AES step function?
a) Add round key
b) Byte substitution
c) Shift rows
d) Mix Columns
Explanation: The correct version in S-AES would be nibble substitution as 4 bits are taken at a time.
6. How many step function do Round 1 and 2 each have in S-AES?
a) 4 and 3
b) Both 4
c) 1 and 4
d) 3 and 4
Explanation: Round 1 has four step functions whereas Round 2 has three step functions.
7. For a key 25D5 and PT input A479 what is the output we obtain after the “add round key” function?
a) F34D
b) 81AC
c) 79DF
d) 327D
Explanation: Simply apply XOR to the state matrix PT with the key matrix to obatain the output which in this case is 81AC.
8. The output of the previous question, on passing through “nibble substitution” gets us the output
a) 3267
b) 1344
c) 64C0
d) CA37
Explanation: 81AC after passing through the “nibble substitution” round produces an output 64C0. A corresponding substitution is referred to in this step.
9. The output of the previous question on passing through the “shift row” step function gives us the output
a) C046
b) 0C64
c) 64C0
d) 640C
Explanation: 64C0 after passing through the “shift row” round produces an output 640C. A one nibble shift is performed in the second row in this step.
10. The output of the previous question on passing through the “mix columns” step function gives us the output
a) 3252
b) 3743
c) 3425
d) 3473
Explanation: 64C0 after passing through the “mix columns” round produces an output 3473. This is obtained by multiplying this matrix with the matrix 1441.