Lemma rt2_equiv : forall n : nat, (n < 256)%nat -> let b := nth n inv_sbox Int.zero in (* (0x0d, 0x0b, 0x0e, 0x09) *) nth n RT2 Int.zero = word_to_int (ff_mult b (Int.repr 13), ff_mult b (Int.repr 11), ff_mult b (Int.repr 14), ff_mult b (Int.repr 9)).