I ran a server for me and friends and items kept getting robbed from players, I then coded this as a fun fix to that. It is possible for anyone to guess the pin to a chest but with the damage upgrade, they would probably die multiple times before being able to get the right pin. This plugin is not meant to completely stop people from stealing from chests instead just add some security to them.
This plugin will also stop people using hoppers to remove items from locked chests and you will not be able to break the chest without using the "Remove Lock" item.
I do not have plans of updating this plugin however I might do in future to update it to newer versions or if there are suggestions in the comments. If there are any bugs put them in the comments and I will (try to) fix them.
To see all crafting recipes. Do /recipes (No Permission)
To open a chest without the pin. Do /open ("pwchest.admin") You need to look at the chest.
To spawn in a custom item. Do /item ("pwchest.admin")