“…SD access control strategies in the open network environment mainly include: SD file operation action control: users at different levels have different permissions for different SD documents, including read, write, preview, execute, share, delete, edit, copy, print and other access permissions. Support the times limit of operation authority, such as the read-only times, forwarding times, copying times, printable copies, and copyable words of SD files; Time constraints on SD files, including start time, end time and cumulative times [10][11].…”