OK so the main idea is, a basic chest, except with more blast resistance, made the same way, but with iron.
second part of the idea is for multiplayer is that after you make the chest you can put a combination on it by crafting it with 3 buttons in the crafting table to add a 3 digit combination, and the chest cant be destroyed without it being unlocked,
Not new? It's not flipping original! There are posts nearly exactly identical to this one, which have been locked. There is nothing wrong with making a new topic on an idea that's been suggested before IF and ONLY IF you make it unique and address issues, which this post has done neither. None of the important issues have been addressed, like how do you deal with people placing a locked chest in front of your house door? You wouldn't be able to break it, you'd have to get an admin to help or move your house or build over it. It's an appealing concept, but when people realize how complicated it becomes, the threads die and these forum spawn crawl up from their hidey holes and start the cycle all over again without doing a basic search to learn why they died.