Editing Confusion and diffusion (section)

===Analysis of AES===
{{Unreferenced section|date=June 2019}}The [[Advanced Encryption Standard]] (AES) has both excellent confusion and diffusion. Its confusion look-up tables are very non-linear and good at destroying patterns.<ref>{{Cite book|title=Cryptography and Network Security: Principles and Practice, Global Edition|last=William|first=Stallings|publisher=Pearson|year=2017|isbn=978-1292158587|pages=177}}</ref> Its diffusion stage spreads every part of the input to every part of the output: changing one bit of input changes half the output bits on average. Both confusion and diffusion are repeated multiple times for each input to increase the amount of scrambling. The secret key is mixed in at every stage so that an attacker cannot precalculate what the cipher does.
None of this happens when a simple one-stage scramble is based on a key. Input patterns would flow straight through to the output. It might look random to the eye but analysis would find obvious patterns and the cipher could be broken.