WPS (Wi-Fi Protected Setup)

Wi-Fi Protected Setup (WPS; originally Wi-Fi Simple Config) is a computing standard that attempts to allow easy establishment of a secure wireless home network.

WPS Supports four usage modes aimed at a home network user adding a new device to the network:

1.PIN Method, in which a personal identification number (PIN) has to be read from either a sticker or the display on the new wireless device. This PIN must then be entered at the "representant" of the network, usually the access point of the network. Alternately, a PIN on the Access Point may be entered into the new device. The PIN Method is the mandatory baseline mode; every Wi-Fi Protected Setup certified product must support it.

2.Push-Button-Method, in which the user simply has to push a button, either an actual or virtual one, on both the access point (or a registrar of the network) and the new wireless client device. Support of this mode is mandatory for access points and optional for connecting devices.

3.Near-Field-Communication Method, in which the user simply has to bring the new client close to the access point to allow a near field communication between the devices. NFC Forum compliant RFID tags can also be used. Support of this mode is optional.

4.USB Method, in which the user uses a USB flash drive to transfer data between the new client device and the access point of the network. Support of this mode is optional, but deprecated.
The last two modes are usually referred as out-of-band methods as there is a transfer of information by a channel other than the Wi-Fi channel itself. Only the first two modes are currently covered by the Wi-Fi Protected Setup certification.

Basic Components in WPS network:

1.Registrar: A device with the authority to issue and revoke credentials to a network. A registrar may be integrated into a wireless access point (AP), or it may be separate from the AP.
2.Enrollee: A device seeking to join a wireless network.
3.AP: An AP functioning as a proxy between a registrar and an enrollee.

Basic scenario that involves AP with internal registrar and STA:

1.AP with internal registrar capabilities configures an Enrollee Station (STA). A descriptive information is transferred through a new Information Element (IE) that is added to the beacon, probe response and optionally to the probe request and association request/response messages. After the identification of the device's capabilities on both ends, a human trigger (Software/ Hardware Push button/PIN) is used to initiate the actual session of the protocol.

2.The session consists of 8 EAP request/response messages will be exchanged on the wireless medium between AP and STA, upon on a successful session, a configuration message (sent to enrolle) to indicate the protocol is done ending with the AP disassociating from the STA .

3.STA waits to reconnect with its new configuration (handed to it by the AP just before).