Question

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}

The question was asked in examination.

This interesting question is from The AES Algorthm topic in section Advanced Encryption Algorithm and Block Cipher Operation of Cryptograph & Network Security

Answer 1

Correct choice is (a) {62 63 63 63}

The best I can explain: Applying the key algorithm we get,

w(0) = {00 00 00 00}; w(1) = {00 00 00 00}; w(2) = {00 00 00 00}; w(3) = {00 00 00 00};

w(4) = {62 63 63 63}; w(5) = {62 63 63 63}; w(6) = {62 63 63 63}; w(7) = {62 63 63 63}.