# Pseudorandom Number Generator and Stream Ciphers MCQs

1. Using the Linear Congruential Method (LCM), for a=7, c=0 and m=32. The period is.

A. 13.

B. 4.

C. 11.

D. 7.

2. Using the Linear Congruential Method, for a=5, c=0 and m=32. The period is.

A. 8.

B. 4.

C. 9.

D. 11.

3. The appropriate value for m (in LCM) is.

A. 2(31) – 1.

B. 2(31).

C. 2(32).

D. 2(32) – 1.

4. A CSPRBG is defined as one that passes the __ test..

A. Runs test.

B. Maurer's Universal statistical test.

C. Frency Test.

D. On-bit test.

5. Find the first 8 bits for Blum Blum Shub Bit Generator when seed = 101355 and n = 192649..

A. 10101010.

B. 11100010.

C. 11001011.

D. 11001110.

6. Which of these modes is an appropriate mode for PRNG?.

A. ECB.

B. CBC.

C. CFB.

D. CTR.

7. Which mode is recommend for the X9.82 Random number generator?.

A. OFB.

B. CBC.

C. CFB.

D. CTR.

8. AES PRNG produces bits outputs of size.

A. 512 bits.

B. 128 bits.

C. 256 bits.

D. 64 bits.

9. Which mode is recommend for the ANSI standard X9.82 Random number generator?.

A. OFB.

B. CTR.

C. CFB.

D. CFB.

10. The CTR algorithm for PRNG is known as.

A. CTR_PRNG.

B. X-SESS.

C. CTR-SESS.

D. CTR_DRBG.

11. Which mode is recommend for the RFC 4086 Random number generator?.

A. CFB.

B. CBC.

C. OFB.

D. CTR.

12. Which mode is less prone to decryption : PRNG using CTR / PRNG using OFB?.

A. OFB.

B. CTR.

C. Both are equally prone.

D. Both can't be decrypted.

13. ANSI X9.17 uses a seed of size.

A. 56 bits.

B. 64 bits.

C. 32 bits.

D. 128 bits.

14. How many 3DES blocks are present in the ANSI X9.17 PRNG?.

A. 2.

B. 3.

C. 4.

D. 5.

15. How many DES encryptions take place in the ANSI X9.17 PRNG?.

A. 3.

B. 6.

C. 9.

D. 12.

16. How many keys are used in the ANSI X9.17 PRNG?.

A. 3.

B. 2.

C. 4.

D. 6.

17. Which of the following PRNGs is used in most recent Intel Chips?.

A. ANSI X9.17 PRNG.

B. NIST CTR_DRBG.

C. ANSI standard X9.82.

D. None of the mentioned.

18. For the NIST CTR_DRBG , Seed length =

A. Output Block Length.

B. Reseed Interval.

C. Reseed Interval + Output Block Length.

D. Output Block Length + Key Length.

Answer= Output Block Length + Key Length

19. The CTR mode uses a Key K and an Initial Vector V. The Intel Digital Random Number generator has these values initially as.

A. K = 0 ; V = 1.

B. K = 0 ; V = 0.

C. K = 1 ; V = 1.

D. K = 1 ; V = 0.

Answer= K = 0 ; V = 0

20. What is the Seed length (seedlen) length for AES-192 ?.

A. 428.

B. 384.

C. 320.

D. 512.

21. What is the Seed length (seedlen) length for 3DES?.

A. 284.

B. 260.

C. 232.

D. 216.

22. The Generate function precedes the Update phase in CTR_DRBG..

A. TRUE.

B. FALSE.

C. Nothing can be said.

D. None of the mentioned.

23. With reference to stream ciphers, the output of the generator is called.

A. Byte Stream.

B. Re-Seed Interval.

C. Key Length.

D. Keystream.

24. Which of the following is not a valid design parameter to be considered in designing stream ciphers?.

A. Keystream should be truly as random as possible.

B. Encryption sence should have a large value.

C. Output of the PRNG (the key) should be sufficiently large.

D. All of the mentioned are valid points that should be considered while designing stream cipher blocks.

Answer= All of the mentioned are valid points that should be considered while designing stream cipher blocks

25. Which mode is recommend for the NIST SP 800-90 Random number generator?.

A. OFB.

B. CBC.

C. CFB.

D. CTR.

26. ANSI X9.17 uses which cryptographic algorithm?.

A. DES.

B. AES.

C. RC5.

D. 3DES.

27. Pretty Good Privacy(PGP) uses which PRNG?.

A. ANSI X9.82.

B. RFC 4086.

C. NIST SP 800-90.

D. ANSI X9.17.

28. Which of the following statements are true? i) Stream Ciphers are fasters than Block Ciphers ii) Block Ciphers can reuse keys iii) Block ciphers use lesser code than stream ciphers.

A.  1st and 2nd.

B.  1st only.

C.  2nd and 3rd.

D.  All are true.

29. Which of the following statements are true? i) RC4 is used in SSL/TLS ii) File transfer, e-mail  use stream ciphers iii) Browser/Web Links use stream ciphers.

A.  1st and 2nd.

B.  1st only.

C.  1st and 3rd.

D.  All are true.

30. Which  of the following statements are true? i) PRNGs are slower than TRNGs ii) PRNGs are periodic iii) TRNGs are nondeterministic.

A.  1st and 2nd.

B.  1st only.

C.  2nd and 3rd.

D.  All are true.

31. Deskewing is a method to modify bit stream to reduce bais that has been developed..

A.  True.

B.  False.

C. Nothing can be said.

D. None of the mentioned.

32. Intel digital random number generator uses which among the following methods to generate random bits?.

A.  pulse detectors of ionizing radiating events.

B.  gas discharge tubes.

C.  wind resistance.

D.  thermal noise.

33. Which of the following AES modes is used in the Intel DRNG? i) AES CFB ii) AES CTR iii) AES CBC iv) AEC OFB.

A. 2nd and 3rd.

B. 3rd and 4th.

C. 1st and 2nd.

D. All of the mentioned.