Android permission mechanism exists obvious safety defects,
i.e., when permissions are authorized to the APP by the user,
the authorization will followed the APP though its whole life
and can not be removed even though the source program is
deleted, which will lead to potential security flaws. To
reduce this risk, it is required that the user has the ability to
distinguish permissions information to decide whether
authorize or not when APP is installed. However, there is no
doubt that it is rather difficult for ordinary users. For the
hidden safe troubles that may be caused by the permissions
mechanism, the Android system gives only sketchy
permissions prompt interface during APP installation, as
shown in figure 2.