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DES Feistel Network
DES is a 16-round Feistel network. This means that the original key is broken up into 16 round keys and that the round function uses 16 iterations.
The round function of DES has four steps:
- Expansion
- Key Mixing
- Substitution
- Permutation
While all the steps are important, we will be focusing on the "substitution" step in this course, as it provides the core security of DES.
For more detail, read about the other steps in the DES round function.