Minecraft wiki entry for Trapped_Chest, associated text: A trapped chest can be "locked" by setting the trapped chest's Lock tag. If a trapped chest's Lock tag is not blank, the trapped chest cannot be opened except by players holding an item with the same name as the Lock tag's text. A trapped chest's Lock tag can be set or unset with the data command. For example, to lock a trapped chest at (0,64,0) so that only players holding an item named "Alice's Key" can open the trapped chest, use data merge block 0 64 0 {Lock:"Alice's Key"}.