From the course: Symmetric Cryptography Essential Training

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Feistel networks

Feistel networks

From the course: Symmetric Cryptography Essential Training

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Feistel networks

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- [Instructor] While they're not used in every case, Feistel networks are fundamental structures for block ciphers. They're named after Horst Feistel who worked in the field of cryptography in the 1970s at IBM and whose work led to the data encryption standard which we'll cover shortly. Feistel networks are a really nice way of combining permutations and substitutions, which are applied to the plaintext repeatedly in a set of iterations called rounds. Each time this package of permutations and substitutions, which we call the round function, is applied to a plaintext block, that's one of those rounds. Within each of these rounds, Feistel networks use the sub key or round key, which are smaller keys derived from the main key with something called a key schedule. The key schedule isn't like a meeting schedule, but it's just a method for extracting and combining bits of the main key to produce the bits of these smaller round keys. Feistel networks have the convenient property that the…

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