rted with the WEP mechanism. Because of its weaknesses, it was supplanted by the WPA1 mechanism and then by the WPA2 mechanism. The mechanisms WPA1 and WPA2 constitute the RSN (Robust Security Network) architecture. The three mechanisms WEP, WPA1 and WPA2 specifically implement third-party access control and data protection services (confidentiality and integrity control). For the WEP mechanism, third-party access control is based on the RC4 (Rivest Cipher) algorithm. Access control takes place during the authentication phase, which is a procedure associated with the MAC data link protocol. The WPA1 and WPA2 mechanisms use the 802. 1x mechanism described in Chapter 6 for access control. The authentication WPA phase is preceded by the procedure putting the security policy in agreement between the access point and the station, during the association phase. For the WEP and WPA1 mechanisms, encryption is executed by the RC4 algorithm. For the WEP mechanism, the master key (MK) is used for the encryption of each Wi-Fi frame. For the WPA1 mechanism, encryption is obtained using a temporary key derived from the MK. In association with encryption, a protocol is added to the MAC data link layer: - WEP protocol in the case of the WEP mechanism; - temporal key integrity protocol (TKIP) in the case of the WPA1 mechanism. MAC Layer For the WPA2 mechanism, encryption is based on the advanced encryption standard (AES) algorithm and the header of the MAC data link protocol is completed by the CCMP (Counter-mode/Cipher block chaining MAC (Message Authentication Code) Protocol) header. In the case of the WEP mechanism, the integrity control is provided by a cyclic redundancy check (CRC) encrypted with the RC4 algorithm. In the case of the WPA1 mechanism, integrity control uses the MICHAEL algorithm. In the case of the WPA2 mechanism, integrity control is obtained using the AES encryption algorithm. 2.3.2. Security policies The security policies supported by the access point are transmitted in BEACON and PROBE RESPONSE frames durin