A. In a modern block cipher, we often need to use a component in the decryption cipher that is the inverse of the component used in the encryption cipher. What is the inverse of each of the following...

A. In a modern block cipher, we often need to use a component in the decryption cipher that is the inverse of the component used in the encryption cipher. What is the inverse of each of the following components?

a. swap b. shift right c. combine

B. In each round of DES, we have all components defined in Figure 10.8 in the text. Which components use a key and which components do not?