Guide to Feistel Ciphers

Feistel networks are one of the easiest ways to build pseudorandom permutations. Thanks to this property, many secret key algorithms (symmetric ciphers) have been designed as Feistel networks, and it is possible to design many others. The most famous of them is probably the Data Encryption Standard algorithm, a former U.S. National Institute of Standards and Technology standard block cipher, origi...