Symmetric Ciphers Questions and Answers – RC4 and RC5 – I

This set of Cryptography Multiple Choice Questions & Answers (MCQs) focuses on “RC4 and RC5”.

1. Which of the following is true for the RC5 algorithm?
i) Has variable number of rounds
ii) Has fixed Key length
iii) High memory Requirements
iv) 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)
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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
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3. The number of rounds in RC5 can range from 0 to _____________
a) 127
b) 63
c) 255
d) 31
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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
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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
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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
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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
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8. The value of the golden ratio is
a) ᶲ =2.618
b) ᶲ =1.622
c) ᶲ =1.743
d) ᶲ =1.618
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9. In RC5, the initialization operations makes use of magic constants defined as follows:
P_w=Odd[(e-2) 2^w].
Q_w=Odd[(φ-1) 2^w].
What is the hexadecimal value of Pw for word size of 16 bits?
a) B7DF
b) B7D4
c) B7E1
d) B6E2
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10. In RC5, the initialization operations makes use of magic constants defined as follows:
P_w=Odd[(e-2) 2^w].
Q_w=Odd[(φ-1) 2^w].
What is the hexadecimal value of Qw for word size of 32 bits?
a) 9D3779B4
b) 9D7779F9
c) 9E36D9B2
d) 9E3779B9
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11. Calculate the number of subkeys required in RC5 for 18 rounds of computation.
a) 40
b) 38
c) 36
d) 34
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Sanfoundry Global Education & Learning Series – Cryptography and Network Security.

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