Symmetric Ciphers Questions and Answers – The AES Algorthm – III

This set of tough Cryptography Questions focuses on “The AES Algorthm – III”.

1. How many computation rounds does the simplified AES consists of?
a) 5
b) 2
c) 8
d) 10
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2. For the case of Mixed Columns and Inverse Mixed Columns, is it true that b(x) = a^-1(x)mod(x⁴ + 1)
where a(x) = {03}x³ + {01}x² + {01}x + {02} and b(x) = {0B}x³ + {0D}x² + {09}x + {0E}
a) True
b) False. The expression for a(x) is wrong.
c) False. The expression for b(x) is wrong.
d) False. Both a(x) and b(x) are faulty.
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3. For an inputs key of size 128 bits constituting of all zeros, what is w(7) ?
a) {62 63 63 63}
b) {62 62 62 62}
c) {00 00 00 00}
d) {63 63 63 62}
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4. On comparing AES with DES, which of the following functions from DES does not have an equivalent AES function?
a) f function
b) permutation p
c) swapping of halves
d) xor of subkey with function f
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5. On perform the Mix Columns transformation for the sequence of bytes “77 89 AB CD” we get output
a) {01 55 EE 4A}
b) {0A 44 EF 4A}
c) {08 55 FF 3A}
d) {09 44 DD 4A}
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6.On perform the Mix Columns transformation for the sequence of bytes “67 89 AB CD” we get output
a) {08 55 FF 18}
b) {28 45 EF 08}
c) {28 45 FF 18}
d) {25 35 EF 08}
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7. Is the following matrix the inverse matrix of the matrix used in the mix columns step?
x³ + 1 x
x x³ + 1

a) Yes
b) No
c) Can’t say
d) Insufficient Information
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8. For the cipher text 0000 0111 0011 1000 and Key 0110 1111 0110 1011, apply the Simplified AES to obtain the plaintext. The plain text is
a) 0110 1001 0111 0001
b) 0110 1111 0110 1011
c) 0010 1001 0110 1011
d) 1111 0101 0111 1111
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9. What is the block size in the Simplified AES algorithm?
a) 8 bits
b) 40 bits
c) 16 bits
d) 36 bits
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10. What is the key size in the S-AES algorithm?
a) 16 bits
b) 32 bits
c) 24 bits
d) None of the mentioned
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11. S-AES and S-DES were both developed by the same person as an educational cryptography system to teach students
a) True
b) False
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12. Which of the following is a faulty S-AES step function?
a) Add round key
b) Byte substitution
c) Shift rows
d) Mix Columns
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Sanfoundry Global Education & Learning Series – Cryptography and Network Security.

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