I’m primarily interested in how substitution permutation works from a process standpoint, but a full breakdown would be cool.
In: Technology
[This comic is a good explanation for the whole process](http://www.moserware.com/2009/09/stick-figure-guide-to-advanced.html)
As for the Substitution Permutation thing.
I think the thing that really trips up a lot of people is that the key is not really involved in these steps.
There’s a substitution table, you can look it up in google, everyone on earth uses the same one. It doesn’t depend on the key or the message.
You look up what to replace with what.
Then the permutation steps shuffles it, and everyone on earth shuffles it the same way.
Only after you done, do you involve the key.
The substitution and the shuffling aren’t providing security on their own, they’re just making it harder for people to figure out the key.
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