# RC4 and RC5 Algorithms MCQs

1. Which of the following is true for the RC5 algorithm?i) Has variable number of roundsii) Has fixed Key lengthiii) High memory Requirementsiv) Uses only primitive computational operations commonly found on microprocessors.

A. i) and iv).

B. i) ii) and iv).

C. iv).

D. i) ii) and iii).

2. What are the allowable values of word size in bit for RC5 algorithm?.

A. 16, 32.

B. 16, 32, 64.

C. 8, 16, 32.

D. 16, 32, 48.

3. The number of rounds in RC5 can range from 0 to _____________.

A. 127.

B. 63.

C. 255.

D. 31.

4. The standard/nominal version of the RC5-w/r/b has parameters w/r/b as.

A. 32/18/16.

B. 16/18/16.

C. 32/12/16.

D. 32/16/18.

5. The total number of subkeys t used in the RC5 algorithm is given by the formula (r corresponds to number of rounds).

A. t=2r+4.

B. t=2r.

C. t=2r+2.

D. t=2r-2.

6. RC5 uses 2 magic constants to define their subkeys. These are.

A. Base of natural Logarithm and Golden ratio.

B. Base of natural Logarithm and Pi.

C. Golden Ratio and  Pi.

D. Pi and Golden Ration.

Answer= Base of natural Logarithm and Golden ratio

7. The value of the base of natural logarithms is.

A. e= 2.7073.

B. e= 2.7183.

C. e= 3.7183.

D. e= 1.7273.

8. The value of the golden ratio is.

A. ? =2.618.

B. ? =1.622.

C. ? =1.743.

D. ? =1.618.

9. In RC5, the initialization operations makes use of magic constants defined as follows:P_w=Odd[(e-2) 2w].Q_w=Odd[(?-1) 2w].What is the hexadecimal value of Pw for word size of 16 bits?.

A. B7DF.

B. B7D4.

C. B7E1.

D. B6E2.

10. In RC5, the initialization operations makes use of magic constants defined as follows:P_w=Odd[(e-2) 2w].Q_w=Odd[(?-1) 2w].What is the hexadecimal value of Qw for word size of 32 bits?.

A. 9D3779B4.

B. 9D7779F9.

C. 9E36D9B2.

D. 9E3779B9.

11. Calculate the number of subkeys required in RC5 for 18 rounds of computation..

A. 40.

B. 38.

C. 36.

D. 34.

12. RC5 encryption uses Right shift and decryption uses Left shift..

A. TRUE.

B. FALSE.

C. Nothing can be said.

D. None of the mentioned.

13. RC5 uses the Feistel Structure..

A. TRUE.

B. FALSE.

C. Nothing can be said.

D. None of the mentioned.

14. Which one of the following is not a RC5 mode of operation?.

A. RC5 block cipher.

B. RC5-Cipher Block Chaining.

D. RC5-CipherText Stealing.

15. Which RC5 mode will have the ciphertext longer than the plaintext by at most the size of a single RC5 block?.

A. RC5 block cipher.

B. RC5-Cipher Block Chaining.

D. RC5-CipherText Stealing.

16. Which RC5 mode of operation is this?.

A. RC5 block cipher.

B. RC5-Cipher Block Chaining.

D. RC5-CipherText Stealing.

17. Which of these is not a characteristic of block ciphers?.

A. Variable key length / block size / number of rounds.

B. Mixed operators, data/key dependent rotation.

C. Key independent S-boxes.

D. More complex key scheduling.

18. Which one of the following RC4 algorithm not used in?.

A. SSL.

B. TLS.

C. FTP.

D. WEP.

19. Till when was the RC4 algorithm kept a secret?.

A. 1990.

B. 1992.

C. 1996.

D. 1994.