Open System Security

The 802.11 standard provides security through two primary methods:
authentication and encryption.
Authentication is the mechanism by which one wireless workstation is
verified to have authorization to talk to a second wireless workstation
within a specific WLAN area. Authentication is created between the access
point and each wireless workstation when in “infrastructure mode.” Authentication has two specific modes: open system and shared key.

As described earlier, an open system allows any wireless workstation to
request authentication, whereas the wireless workstation receiving the
request may enable any authentication for any request. It may also
enable access from only those wireless workstations on a user-defined list.
A shared system, however, only allows wireless workstations that
have a secret encrypted key that can be authenticated. Note that
shared-key authentication is only possible for systems that have an
optional level of encryption functionality.