AES?CCMP is the strongest security in development for IEEE 802.11i. This chapter looks at why AES was chosen and at its credentials as an encryption algorithm. Security systems use AES in conjunction with an operating mode; some of the simpler and more common modes are covered here. We then introduce CCMP, the protocol used with IEEE 802.11, and explain how it is implemented in practice. This chapter shows how CCMP fits into the IEEE 802.11 framework and provides state-of-the-art security for the most demanding users.