Lockable Shulker Boxes (Iron Vaults)

This would be a shulkerbox made out of iron that can hold the same amount of items as a normal box. The crafting recipe would be the same as a shulker box, but with iron blocks on the side. 

To open the iron vault, you need a key. To craft a key, you need one iron ingot and a redstone dust. The dust goes in the middle and the ingot goes under it. If a vault doesn't have a key attached to it, you simply right click it to open it, then there is a slot to the side where you put the key. The key then returns to your inventory and only that key can open the vault. 

The vault can of course be broken but they will still act as shulker boxes and only drop themselves. If you play with friends and you want to keep some things a bit safer you can use vaults. Renaming a key in an anvil should be possible and the vault should still know that it's that key that's being used.

It might seem like this feature makes normal shulker boxes useless, but since you need to have the keys in your inventory, you wouldn't be able to have that many with you. I think it's somewhat balanced, probably could be improved with a bit work. 

Hope you like the idea! :)