The AES cipher begins and ends with an)_________ stage because any other stage, applied at the beginning or end,is reversible without knowledge of the key and would add no security.
A)Substitute bytes
B)AddRoundKey
C)MixColumns
D)ShiftRows

Question

Quizplus · Accepted Answer

The AddRoundKey stage is the only stage that involves the secret key, making it the only irreversible stage. Therefore, it is necessary to apply it both at the beginning and end of the cipher. The other stages (Substitute bytes, ShiftRows, and MixColumns) are reversible and could be applied in different orders or omitted without affecting the security of the cipher.

The AES Cipher Begins and Ends with An)_________ Stage Because