WPA-PSK - CCMP Mode

這裡記錄一下當使用者設定成WPA-PSK - CCMP的時候，它的封包流程和內容長什麼樣子。

AP MAC Address: 00:12:0E:C1:D7:09
STA MAC Address: C0:FF:D4:D4:E9:BA

Security: WPA1 Personal
Cipher Suite: CCMP
Pre-Shared Key: 0987654321

#119: The STA send Probe Request to AP.
#122: The AP feedback Probe Response to STA.
#123: The STA send Authentication (request) to AP.
#125: The AP feedback Authentication (response) to STA.
#127: The STA send Association Request to AP.
#129: The AP feedback Association Response to STA.
#141, #143, #145, #151: Unicast 4-Way handshaking.
#155, #159: Multicast / Broadcast 2-Way handshaking.
#165: Data packet; decrypted is a DHCP Offer.

基於TKIP的經驗，這回直接看Probe Response封包：
#122: The AP feedback Probe Response to STA.

由上圖資訊可以得知：

• OUI: 00:50:F2 (Microsoft Corp. ；這是微軟的OUI)
• WPA Version: 1
• Multicast Cipher Suite Type: AES (CCM) (4)
• Unicast Cipher Suite: AES (CCM) (4)
• Authentication Key Management Type: PSK (2)

AES (Advanced Encryption Standard；進階加密標準)和CCMP (Counter Mode with CBC-MAC Protocol；計數器模式與密碼塊鏈資訊認證)就某種程度上而言是一模一樣的東西。IEEE 802.11的定義如下：

#165: Data packet; decrypted is a DHCP Offer.

這一個Data封包，多了一個CCMP Parameters的欄位資訊，表示是由CCMP來加密。

由此可見，WPA TKIP和CCMP的差異就在於Multicast / Unicast的Ciphrt Suite。

Refer: CWSP – CCMP Encryption Method

Releated: WPA-PSK - TKIP Mode