Important

This does not prevent the chest/ hopper from being destroyed, the plugin has to be combined with some other grief protection to prevent unauthorized access of the chests. It also allows anyone who manages to steal the key or guess the password to access the chests. The server this was originally created for allowed stealing, but used mining fatigue in enemy bases to make it more difficult.

How to use

To lock a chest rename a tripwire hook with the desired password and shift+right click the chest with that tripwire hook. After that the chest has been locked it can only be opened when holding an item that has been renamed the same as the tripwire hook. To remove the lock again just shift+right click the chest again with the tripwire hook.

Chests can still output items into hoppers and vice versa if the chest and hopper are locked with the same password.
Only adding and removing the lock requires a tripwire hook, opening the chest can be done with any item renamed to the correct password.