1. What is the correct order of operation within each round of the Whirlpool algorithm?
a) Add round key, Substitute bytes, Mix rows, Shift columns
b) Substitute bytes, Add round key, Shift columns, Mix rows
c) Mix rows, Substitute bytes, Shift columns, Add round key
d) Substitute bytes, Shift columns, Mix rows, Add round key
Answer
Answer: d [Reason:] The correct order is Substitute bytes, Shift columns, Mix rows, Add round key.
2. What is the size of the s-box table/matrix in Whirlpool?
a) 8 × 8
b) 16 × 16
c) 8 × 16
d) 16 × 8
Answer
Answer: b [Reason:] The size of the matrix is 16 × 16.
3. The S-box implements linear mapping thus providing diffusion.
a) True
b) False
Answer
Answer: b [Reason:] Non-linear mapping provides diffusion. The s-box provides Non-linear mapping.
4. Another name for the Whirlpool key is
a) CState
b) LState
c) Estate
d) KState
Answer
Answer: d [Reason:] Whirlpool uses a 512 bit key called KState.
5. How many round constants (RCs) are required in Whirlpool?
a) 10
b) 11
c) 12
d) 21
Answer
Answer: a [Reason:] There are 10 RCs required for modifying 10 Keys in each step.
6. The Round Constant is dependent on the s-box values.
a) True
b) False
Answer
Answer: a [Reason:] The Round Constant is given by S[8(r-1)+j] where S is the s-box permutation.
7. The Round Constant is given by S[8(r-1)+j]. What are the limits of ‘r’?
a) 0 <= r <= 11
b) 0 <= r <= 12
c) 0 <= r <= 10
d) 0 <= r <=16
Answer
Answer: c [Reason:] r can have values from 0 to 10.
8. When the Round Constant is given by S[8(r-1)+j]. What are the limits of ‘i’ and ‘j’?
a) i = 1 ; 0 <= j <= 7
b) i = 0 ; 0 <= j <= 7
c) 0 <= i <= 7; 0 <= j <= 7
d) 0 <= i <= 7; j=0
Answer
Answer: b [Reason:] All rows except the first one are 0 i.e. RC=0 for ‘i’ not equal to 0.
9. The 7th row in the 8 × 8 matrix undergoes a ___________ shift.
a) 6 bit
b) 6 byte
c) 7 bit
d) 7 byte
Answer
Answer: b [Reason:] The nth row in the 8 × 8 matrix undergoes an (n-1) byte shift.
10. How many XOR gate operations are involved in the S-box permutation?
a) 12
b) 8
c) 16
d) 4
Answer
Answer: a [Reason:]12 XORs are involved in the S-box permutation in Whirlpool.
11. Which round provides linear diffusion in the Whirlpool Algorithm?
a) Add Key
b) Substitute Bytes
c) Mix Rows
d) Shift Rows
Answer
Answer: c [Reason:] MR function is the linear diffusion layer of the Whirlpool block cipher.
