Cryptography Teacher Question:

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}

Cryptography Teacher Interview Question
Cryptography Teacher Interview Question

Answer:

b) {28 45 EF 08}
Explanation: Perform the mix columns transformation to obtain the output {28 45 EF 0A}.


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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.		What is the block size in the Simplified AES algorithm?
a) 8 bits
b) 40 bits
c) 16 bits
d) 36 bits