docs: def decipher_block (self, state):
          """Perform AES block decipher on input"""
          if len(state) != 16:
              Log.error(u"Expecting block of 16")
  
          self._add_round_key(state, self._Nr)
  
          for i in range(self._Nr - 1, 0, -1):
              self._i_shift_rows(state)
              self._i_sub_bytes(state)
              self._add_round_key(state, i)
              self._mix_columns(state, True)
  
          self._i_shift_rows(state)
          self._i_sub_bytes(state)
          self._add_round_key(state, 0)
          return state