ayload B Integrity Check Value (ICV) Unencrypted Headers Encrypted PDU Other Extended PN,EKS Encrypted Payload B Integrity Check Headers Encrypted Payload A Value (ICV) Unencrypted Headers Encrypted PDU FIGURE 8-4 Multiplexed MAC PDU format [2] Classification of MAC Protection Level Management Messages Confidentiality, Integrity No Protection Integrity Encryption Encryption, ICV FIGURE 8-5 The IEEE 802. 16m management message protection process [2,3] CMAC-based integrity protection: CMAC Tuple (i.e., a keyed message digest to authenticate the sender if authentication is supported) is included with the MAC management message which protects the entire MAC management/control message. The original MAC management message is plain text. AES-CCM based authenticated encryption: the Integrity Check Value (ICV) field is included after encrypted payload and protects the integrity of the payload, as well as the MAC header (see Figure 8-4). CHAPTER 8 The IEEE 802.16m Security Sub-Layer The security context is a set of parameters associated with a key in each hierarchy that defines the scope while the key usage is considered to be secure. Examples of these parameters include key lifetime and counters to ensure that the same encryption will not be used more than once. When the context of the key expires, a new key is obtained to continue operation. The master key context includes all parameters associated with the master key, and is created when EAP authentication is fulfilled. This context is created on completion of successful authentication/reauthentication, and is discarded when no longer valid or if a key agreement procedure was not completed for a period of time [2]. The context is created by the MS and the authenticator when authenticating in radio frame legacy zones or new zones, and is maintained during zone switching. Other security contexts include PMK, AK, TEK, and SA contexts. 8.7 USER PRIVACY The user identity in IEEE 802.16m systems is protected by ensuring that system hackers cannot obtain the mapping between th