Equivalence Classes in AES -- Part 1

Abstract

We investigate properties of equivalence classes in AES which arise naturally from properties of MixColumns and InvMixColumns. These two operations have the property that the XOR of the 4 input bytes equals the XOR of 4 output bytes. We examine the effect on equivalence classes due to the operation of SubBytes, ShiftRows, MixColumns and AddRoundKey. The next phase of research is to find a key recovery attack using known (plaintext, ciphertext) equivalence class pairs. Keywords: AES, Equivalence, Class, MixColumns, ShiftRows, SubBytes, AddRoundKey, Schedule, State, XOR