What is Feistel Cipher

Question

What do you mean by the term Feistel Cipher? Describe in brief.

Answer 1

Feistel ciphers are the special class of iterated block ciphers where the cipher text is computed from the plaintext by repeated application of the similar transformation or round function. Feistel ciphers are as well sometimes termed as DES-like ciphers.

In Feistel cipher, the text being encrypted is split to two halves. The round function ‘f’ is applied to one half by using a sub key and the output of ‘f’ is exclusive-ored with other half. The two halves are then swapped. Each and every round follows the similar pattern except for the last round where there is no swapping.