Cryptography Teacher Question:

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.

Cryptography Teacher Interview Question
Cryptography Teacher Interview Question

Answer:

a) True
Explanation: The statment is true and can be checked as it is similar to the matrix forms of mixed columns and inverse mixed columns.


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Cryptanalysis is used:
A. to find some insecurity in a cryptographic scheme B. to increase the speed C. to encrypt the data D. none of the mentioned		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}