Feistel scheme

Hey little one! Do you like secrets and codes? Well, there is something called the Feistel scheme that helps us keep secrets safe using a code.

You know how we can break things apart into smaller pieces and then put them back together, right? Like how we can take a puzzle apart and then put it back together again. That's kind of like what the Feistel scheme does.

It takes a secret message that we want to protect, and it breaks it apart into little pieces called "blocks". Then, it uses the pieces to create a code that is really hard for anyone to break.

Here's how it does it:

1. First, it takes the secret message and divides it into two equal parts.

2. Then, it takes one of those parts and passes it through something called a "function". This function changes the part in a way that no one can easily undo.

3. Next, it combines the changed part with the other part of the message.

4. Then, it repeats this process over and over again. Each time, it switches which part is passed through the function and which part is combined with the other part.

5. Finally, it puts all the blocks back together into one big code that only someone with a special key can understand.

So, in summary, the Feistel scheme takes a secret message, breaks it apart, mixes it up using a special function, and puts it back together again as a code that only someone with the special key can read. Pretty cool, huh?