Problem
1. We often hear about Feistel and non-Feistel ciphers. Use the literature or the Internet to find out about the main difference between these two types of ciphers. To which category does DES belong?
2. Since the size of the cipher key in DES is small (only 56 bits), one uses triple DES block cipher today. Use the literature and find out how we can change DES to triple DES with only two keys. What is the size of the key in the triple DES?