1. Which among the following cannot be used in the case of stream ciphers?
a) TRNGs
b) PRNGs
c) PRFs
d) All of the mentioned
Answer
Answer: a [Reason:] TRNGs are not practical for stream ciphers.
2. A stream cipher key is usually of size ___ or 128 bits.
a) 56
b) 64
c) 54
d) 48
Answer
Answer: c [Reason:] A stream cipher key is usually of size 54 or 128 bits.
3. Which among the following has the lowest bitrate ?
a) PRF
b) TRNG
c) PRNG
d) All have the same bitrate
Answer
Answer: b [Reason:] TRNGs are the slowest. The mechanism used to generated True Random numbers may not be able to generate bits at a rate sufficient to keep up with the application requiring the random bits.
4. RC4 was built on the sole purpose of generating random bits i.e. to act as a PRNG.
a) True
b) False
Answer
Answer: a [Reason:] The statement is true. RC4 is a purpose built algorithm.
5. Maurer’s Universal Statistical Test is –
a) a test to determine whether the number of runs of ones and zeros of various lengths is as expected
b) a test to detect if a sequence can be significantly compressed without loss of information
c) a test to determine whether the number of ones and zeros in a sequence is approx the same as in a truely random o/p
d) a test for the check of evenness in the 1s and 0s
Answer
Answer: b [Reason:] Maurer’s Universal Statistical Test is a test to detect if a sequence can be significantly compressed without loss of information.
6. Runs Test is
a) a test to determine whether the number of runs of ones and zeros of various lengths is as expected
b) a test to detect if a sequence can be significantly compressed without loss of information
c) a test to determine whether the number of ones and zeros in a sequence is approx the same as in a truely random o/p
d) a test for the check of evenness in the 1s and 0s
Answer
Answer: a [Reason:] Runs Test is a test to determine whether the number of runs of ones and zeros of various lengths is as expected.
7. Frequency Test is
a) a test to determine whether the number of runs of ones and zeros of various lengths is as expected
b) a test to detect if a sequence can be significantly compressed without loss of information
c) a test for the check of evenness in the 1s and 0s
d) a test to determine whether the number of ones and zeros in a sequence is approx the same as in a truely random o/p
Answer
Answer: d [Reason:] Frequency Test is a test to determine whether the number of ones and zeros in a sequence is approx the same as in a truely random o/p.
8. We should not be able to determine the seed from any previous knowledge of the bits sequence. This is the property of backward unpredictability.
a) True
b) False
Answer
Answer: a [Reason:] The statement is true.
9. Forward Unpredictability is a property when the seed is unknown, and the next output bit is the sequence should be unpredictable.
a) True
b) False
Answer
Answer: a [Reason:] The statement is true.
