Here is an article that explains the concept of child keys in BIP32 in a way that is easy to understand, even for a 5 year old:
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What goes on under the hood when we talk about Bitcoin and Ethereum wallets?
Imagine you have a super secret box that you keep your favorite toy in. You want to share it with a friend, but you don’t want anyone else to know what’s inside.
In digital wallets like Bitcoin and Ethereum, there are special “keys” that help control access to the toy (the wallet). But how do they work?
We talk about two types of keys: Child-Kids and Hardened Child-Kids.
Child-Key
Imagine your friend wants to borrow your secret box. You say, “Okay, you can take a look inside, but only for a minute.” It’s like giving them a Child-Key.
A Child-Key is a copy of the original key that doesn’t contain all the information about the toy (wallet). Think of it as a simplified version of the toy. This Child-Key is useful for borrowing things from the owner, but not for storing the actual toys.
Hardened Child-Kids
Now imagine your friend comes back and says, “Hey, I borrowed your secret box, but now I need to keep it safe!” You say, “Okay, here’s a Hardened Child-Key. This has all the information about my toy (wallet) included.”
A Hardened Child-Key is like the original key itself! It’s a special version that includes all the information about the toy (wallet). But unlike a regular Child-Key, a Hardened Child-Key can’t be easily copied or shared with others.
Why are they different?
Think of it this way: if someone had a super long password to get into your secret box, a Child-Key would only give them access for one minute. A Child-Key wouldn’t protect the toy (wallet) itself.
But when you create a Hardened Child-Key, you are creating a special key that can only be used with the actual toy (wallet). This way, even if someone gets a copy of your Hardened Child-Key, they won’t be able to access all of your toys (wallets).
In BIP32
Bitcoin Improvement Proposal 32 (BIP32) is a set of rules for creating and managing digital wallets. In BIP32, child-keys are generated based on the parent key (the original key). The idea is that when you create a wallet, you can choose to use either a Child-Key or a Hardened Child-Key.
When you generate a Child-Key, it’s like creating a simplified version of your toy (wallet). But if you want to store all of your toys (wallets) safely, you need to use a Hardened Child-Key.
So, to summarize: Child-Keys are like simplified versions of the original key, while Hardened Child-Keys are like the original key itself. They are designed to protect your digital assets from unauthorized access and sharing.
Hope this helps!