I was reading about the DISCOVERY operation phase for an RSN. There a diagram shows NULL Authentication (Second Part, in the diagram). What is it and what is the use?
The image is from the book, Cryptography and Network Security: Principles and Practice.
"Open authentication", is fundamentally a NULL authentication where the client says "authenticate me", and the AP responds with "yes". Open authentication is the only method used in enterprise WLAN deployments, it is fundamentally a NULL authentication, Therefore, "real authentication" is achieved by using 802.1X/EAP authentication mechanisms. A typical secure enterprise WLAN AP blocks WLAN client traffic at the AP until a successful 802.1X authentication.
That means that there is no verification of the user or machine. Open Authentication allows any device that places an authentication request to the access point (AP). Open Authentication uses clear-text transmission to allow a client to associate to an AP and therefore 802.1x could be used.