# Secure Hash Algorithms (SHA) MCQs

1. SHA-1 produces a hash value of.

A. 256 bits.

B. 160 bits.

C. 180 bits.

D. 128 bits.

2. What is the number of round computation steps in the SHA-256 algorithm?.

A. 80.

B. 76.

C. 64.

D. 70.

3. In SHA-512, the message is divided into blocks of size ___ bits for the hash computation..

A. 1024.

B. 512.

C. 256.

D. 1248.

4. What is the maximum length of the message (in bits) that can be taken by SHA-512?.

A. 2128.

B. 2256.

C. 264.

D. 2192.

5. The message in SHA-512 is padded so that it's length is.

A. 832 mod 1024.

B. 768 mod 1024.

C. 960 mod 1024.

D. 896 mod 1024.

6. The big-endian format is one in which.

A. the least significant byte is stored in the low-address byte position.

B. the least significant byte is stored in the high-address byte position.

C. the most significant byte is stored in the high-address byte position.

D. the most significant byte is stored in the low-address byte position.

Answer= the most significant byte is stored in the low-address byte position

7. In SHA-512, the registers 'a' to 'h' are obtained by taking the first 64 bits of the fractional parts of the cube roots of the first 8 prime numbers..

A. TRUE.

B. FALSE.

C. Nothing can be said.

D. None of the mentioned.

8. What is the size of W (in bits) in the SHA-512 processing of a single 1024- bit block?.

A. 64.

B. 128.

C. 512.

D. 256.

9. In the SHA-512 processing of a single 1024- bit block, the round constants are obtained.

A. by taking the first 64 bits of the fractional parts of the cube roots of the first 80 prime numbers.

B. by taking the first 64 bits of the fractional parts of the cube roots of the first 64 prime numbers.

C. by taking the first 64 bits of the fractional parts of the square roots of the first 80 prime numbers.

D. by taking the first 64 bits of the non-fractional parts of the first 80 prime numbers.

Answer= by taking the first 64 bits of the fractional parts of the cube roots of the first 80 prime numbers

10. The output of the N 1024-bit blocks from the Nth stage is.

A. 512 bits.

B. 1024 bits.

C. N x 1024bits.

D. N x 512 bits.

11. Among the registers 'a' to 'h' how many involve permutation in each round?.

A. 4.

B. 5.

C. 6.

D. 3.

12. In SHA-3, which step function does the operation L[2,3] <- L[2,3]  XOR NOT(L[3,3]) AND L[4,3] represent?.

A. Theta.

B. Rho.

C. Pi.

D. Chi.

13. In SHA-3, which function does the operation L[2,3]<- C[1]  XOR L[2,3]  XOR  ROT(C[3],1) represent?.

A. Theta.

B. Rho.

C. Pi.

D. Chi.

14. How many rounds are present in each iteration function of SHA-3?.

A. 3.

B. 4.

C. 5.

D. 6.

15. In SHA-3, which step function does not affect W [0, 0]?.

A. Theta.

B. Iota.

C. Pi.

D. Chi.

16. Which among the following is not a substitution operation?.

A. Theta.

B. Iota.

C. Pi.

D. Chi.

17. In SHA-3, for a message digest size of 256, what is the bitrate 'r' (capacity = 512) ?.

A. 576.

B. 1088.

C. 1152.

D. 832.

18. The sponge construction involves 2 phases, these are.

C. absorbing and sezing.

D. none of the mentioned.

19. Within the Keccak function-f, the 1600 bits are arranged into a 5 x 5 x 64 array a. The 64-bit units are referred to as.

A. lemma.

B. z co-ordinate.

C. kernel.

D. lanes.

20. What are the co-ordinates of the bottom-right most lane?.

A. L[4 ,4]..

B. L[4, 0]..

C. L[5, 5]..

D. L[5, 1]..

21. How many iterations / rounds does the Keccak function have ?.

A. 12.

B. 36.

C. 16.

D. 24.

22. Which step function works only W[0, 0]?.

A. Theta.

B. Iota.

C. Pi.

D. Chi.

23. SHA-3 has an advantage over other algorithms because, there is no need for table look ups, arithmetic operations or data dependent operations..

A. TRUE.

B. FALSE.

C. Nothing can be said.

D. None of the mentioned.

24. The registers 'a' and 'e' involve.

A. Permutation and substitution both.

B. Only Permutation.

C. Only substitution.

D. Don't undergo any operations.

25. In SHA-512, W16 is dependent on.

A. W0,W3,W7,W13.

B. W3,W7,W11,W15.

C. W0,W1,W9,W14.

D. W0,W1,W10,W13.

26. In SHA-512, W16 is dependent on.

A. W63,W68,W72,W76.

B. W66,W70,W71,W76.

C. W63,W67,W71,W77.

D. W63,W65,W71,W76.

27. What is the number of operation required to come up with 2 messages having the same message digest in SHA-512?.

A. 2256.

B. 2512.

C. 21024.

D. 2128.

28. The underlying structure of the SHA-3 algorithm is referred to as.

A. Texture construction.

B. Layer construction.

C. Sponge construction.

D. Cement construction.

29. SHA-3 allows variable length input and output..

A. TRUE.

B. FALSE.

C. Nothing can be said.

D. None of the mentioned.

30. Multi-rate padding is denoted by.

A. 10*.

B. 10*1.

C. 10*1*.

D. 0*1.

31. In SHA-3, if the desired output is l bits, then j blocks are produced, such that.

A. (j-1) x r < l <= (j) x r.

B. (j) x r< l <= (j+1) x r.

C. (j-1) x r < l <= (j+1) x r.

D. (j+1) x r < l <= (j+2) x r.

Answer= (j-1) x r < l <= (j) x r

32. In the sponge construction, the value 'c' is known as.

A. constant.

B. capacity.

C. construct.

D. closure.

33. The larger the value of 'r', the lesser the rate at which message bits are processed by the sponge construction..

A. TRUE.

B. FALSE.

C. Nothing can be said.

D. None of the mentioned.

34. We can trade security for speed by.

A. decreasing 'c' and increasing 'r'.

B. increasing 'c' and decreasing 'r'.

C. decreasing both 'c' and 'r'.

D. increasing both 'c' and 'r'.

Answer= increasing 'c' and decreasing 'r'

35. The default values for Keccak f are.

A. c =1024 and r =576.

B. c =786 and r =832.

C. c =512 and r =1088.

D. c =512 and r =832.

Answer= c =512 and r =1088

36. In the Theta step function, which is a substitution step, each bit value changes. Each bit is dependent on _________ other bits for its new value..

A. 13.

B. 4.

C. 7.

D. 11.

37. Which step function provides most amount of diffusion for the Keccak iteration step?.

A. Theta.

B. Rho.

C. Pi.

D. Chi.

38. The Pi step function can be written as

A. (x, y) × (y, (x + y)).

B. (x, y) × (y, (2x + 3y)).

C. (x, 2y) × (y, (2x + 3y)).

D. (x, 2y) × (y, (x + y)).

Answer= (x, y) × (y, (2x + 3y))

39. The CHI step involves which of the following gate operations?.

A. AND and NAND.

B. AND and XOR.

C. XOR and NAND.

D. XOR and XNOR.

40. What are the new co-ordinates for (x, y) in the Rho step for t =3?.

A. (1, 7).

B. (1, 4).

C. (3, 2).

D. none of the mentioned.

41. The Rho function is defined as : a[x, y, z] ? a[x, y, z-g(t)], where g(t) is defined as.

A. (t+1)(t+2)/2.

B. (t+1)(t-2)/2.

C. (t-1)(t-2)/2.

D. (t-1)(t+2)/2.

42. The Chi function is defined as.

A. a[x] ? a[x] XOR ( a[x + 1]XOR 1)  AND a[x+2]).

B. a[x] ? a[x] AND ( a[x + 1]XOR 1)  AND a[x+2]).

C. a[x] ? a[x] AND ( a[x + 1] XOR a[x+2]).

D. a[x] ? a[x] XOR ( a[x + 1]  AND a[x+2]).

Answer= a[x] ? a[x] XOR ( a[x + 1]XOR 1)  AND a[x+2])

43. In SHA-3, the Iota step function has a round constant which only works on the last lane..

A. TRUE.

B. FALSE.

C. Nothing can be said.

D. None of the mentioned.

44. Which is the only step function that provides non-linear mapping?.

A. Theta.

B. Rho.

C. Pi.

D. Chi.