4 (10 points) (a) Give the formulas that define Feistel cipher encryption and decryption (b) Is the TEA cipher a Feistel cipher? Why or why not? (c) The Data Encryption Standard (DES) is a Feistel cipher. What is the round function in DES? 4 (10 points) (a) Give the formulas that define Feistel cipher encryption and decryption (b) Is the TEA cipher a Feistel cipher? Why or why not? (c) The Data Encryption Standard (DES) is a Feistel cipher. What is the round function in DES