Is it possible for IEEE 802.11 WPA/WPA2 not to use Group Cipher? A Wi-Fi AP and client advertise and negotiate WPA/WPA2, RSN Information Element field is used: , highlighted field is used. I wonder that, what if Group Cipher is set to one of Reserved? Does this mean the AP will not use any cipher for broadcast and multicast, and just sends data frames in plaintext? ![enter image description here](

Reserved values are not valid for the standard; they are reserved for future use. The AP and STA will not negotiate a Reserved value. Either receiving a value that it doesn't support should refuse with a status value meaning "Invalid group cipher."

In fact, Vendor-specific was defined in order to prevent non-standard use of Reserved. Of course, both the AP and STA must be able to use the same vendor-specific method before they can agree on its use.