5.3-5.4

In this section, I didn't quite completely understand the whole Rijndael decryption still since I never completely understood the encryption. I sort of get it, but I'm not sure if it is 100% correct. One really cool thing came in 5.4 where they showed how they designed each portion of the cipher to be resistant to something and also had a strict definition for the S-Box. That made it really nice since there isn't really any confusion on how it works.