We use the plugin BlockLocker
To lock a chest, shulker chest, furnace, crafting table, or door just place a sign on it to make it private. To allow redstone items to modify your locked blocks add the [Redstone] tag to the third line of the sign by using /bl 3 [Redstone]. You can also use the same feature to allow other users to access your protected blocks. /bl 3 UserName. Read more on the plugins page for help or ask a Mod/Admin.