A directory of Objective Type Questions covering all the Computer Science subjects. Here you can access and discuss Multiple choice questions and answers for various compitative exams and interviews.

1. In affine block cipher systems if f(m)=Am + t, what is f(m1+m2) ?
a. f(m1) + f(m2) + t
b. f(m1) + f(m2) + 2t
c. f(m1) + t
d. f(m1) + f(m2)
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Answer: (a).f(m1) + f(m2) + t

2. In affine block cipher systems if f(m)=Am + t, what is f(m1+m2+m3) ?
a. f(m1) + f(m2) + f(m3) + t
b. f(m1) + f(m2) + f(m3) +2t
c. f(m1) + f(m2) + f(m3)
d. 2(f(m1) + f(m2) + f(m3))
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Answer: (c).f(m1) + f(m2) + f(m3)

3. What is the number of possible 3 x 3 affine cipher transformations ?
a. 168
b. 840
c. 1024
d. 1344
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Answer: (d).1344

4. Super-Encipherment using two affine transformations results in another affine transformation.
a. True
b. False
c. May be
d. Can't say
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Answer: (a).True

5. If the key is 110100001, the output of the SP network for the plaintext: 101110001 is
a. 110100011
b. 110101110
c. 010110111
d. 011111010
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Answer: (b).110101110

6. If the key is 110100001 where,
If ki=0, then S_i (x)=((1 1 0 | 0 1 1 | 1 0 0 ))x+((1 1 1))
and If ki=1, then S_i (x)=((0 1 1 | 1 0 1 | 1 0 0))x+((0 1 1))
then the output of the SP network for the plaintext: 101110001 is
a. 010110011
b. 111000011
c. 110110111
d. 010110110
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Answer: (a).010110011

7. Confusion hides the relationship between the ciphertext and the plaintext.
a. True
b. False
c. May be
d. Can't say
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Answer: (b).False

8. The S-Box is used to provide confusion, as it is dependent on the unknown key.
a. True
b. False
c. May be
d. Can't say
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Answer: (a).True

9. Which of the following slows the cryptographic algorithm –

1) Increase in Number of rounds
2) Decrease in Block size
3) Decrease in Key Size
4) Increase in Sub key Generation
a. 1 and 3
b. 2 and 3
c. 3 and 4
d. 2 and 4
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Answer: (b).2 and 3

10. DES follows
a. Hash Algorithm
b. Caesars Cipher
c. Feistel Cipher Structure
d. SP Networks
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Answer: (c).Feistel Cipher Structure

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