L5 Data Encryption Standard

block cipher concepts, pseudorandom permutations, Feistel network mechanics, DES structure (S-boxes, f() function, avalanche effect)

How is Confusion introduced in block ciphers?

Through substitution operators like Lookup Tables

How is Diffusion introduced in block ciphers

Through permutation like swapping or mixing bits/bytes

What is DES?

DES (Data Encryption Standard) is a Feistel network with 64-bit block size and 56-bit key.

It is the most studied cipher in history

What is an S-box?

Does non-linear substitution.

input → substitution → output

Introduces confusion

What is a Block Cipher?

A cipher that encrypts in blocks at a time.

What are Pseudorandom Permutations?

Permutation is to re-order/shuffle

A pseudorandom permutation is a function that shuffles bits/bytes in a way that is indistinguishable to a random shuffle

What is a Feistel Network?

A a mechanism to create block ciphers.