When using cell phones and computers, users may encrypt private files (e.g., photos, videos, messages, etc.) or private applications (e.g., Social Network Software, etc.) to prevent the private files or private applications from being used by others. Consequently, privacy leaks are effectively avoided. In practice, the users need to manually select the private files or private applications to perform encryption, and obviously, the efficiency of selection may decrease along with the increase of the quantity of the private files or private applications.