Question

There is an addition of round key before the start of the AES round algorithms.

(a) True

(b) False

This question was posed to me during an interview.

Origin of the question is The AES Algorithm topic in chapter Advanced Encryption Algorithm and Block Cipher Operation of Cryptograph & Network Security

Answer 1

Correct option is (a) True

The explanation: In AES the final round contains only three transformations, and there is an initial single transformation (Add Round Key) before the first round which can be considered Round 0. Each transformation takes 4×4 matrixes as input and produces a 4×4 matrix as output.