Category: Security

Different Authentication types

1. Open
2. PSK
3. 802.1X

Open Authentication – There is no authentication (Free for all). Device connects to wireless network without any issue.  Open Authentication might also redirect to a captive portal like at a Airport or Public Wireless places. There is a two way packet exchange. It is not the secure way to setup the wireless.

PSK / WPA/WPA2 – Preshared Key – Authentication using a set password on the network. Used in small/medium and mostly home deployments. Also deployed in secondary wireless network in organizations.
There is no additional requirements for authentication. PSK can be subjected to dictionary attacks. Suggested to change the PSK regularly. Recently there was an outbreak for WPA2 Krack attack (https://www.krackattacks.com/) You can setup a phrase or lengthy password. Consists of WPA/WPA2 Personal.

802.1X / WPA2 Enterprise – Strongest of all the authentication types. Framework which defines authentication, there is a Supplicant(Client which wants to connect), Authenticator(AP/Controller) and Authentication Server(Radius, ISE etc). Advantageous if there are more than 1 radius servers as a backup if primary server is not available due to any reason. Different EAP (Extensible Authentication Protocol) types are used in this setup. EAP method used (Credentials/Certificate/SIM Card etc) will be defined for the user authentication to the wireless network.

Upcoming Authentication Types in near future

SAE – Simultaneous Authentication of Equals – SAE is resistant to passive attack, active attack, and dictionary attack. It provides a secure alternative to using certificates or when a centralized authority is not available.
DPP – Device provisioning protocol – authenticate device without password like QR code, some kind of tag etc. Applies to lot of IoT devices which do not have screen for authentication.
WPA3 – The new WPA3 security standard is expected to land in devices later in 2019. our new capabilities for personal and enterprise Wi-Fi networks will emerge in 2018 as part of Wi-Fi CERTIFIED WPA3™. Two of the features will deliver robust protections even when users choose passwords that fall short of typical complexity recommendations, and will simplify the process of configuring security for devices that have limited or no display interface. Another feature will strengthen user privacy in open networks through individualized data encryption. Finally, a 192-bit security suite, aligned with the Commercial National Security Algorithm (CNSA) Suite from the Committee on National Security Systems, will further protect Wi-Fi networks with higher security requirements such as government, defense, and industrial. (https://www.wi-fi.org/news-events/newsroom/wi-fi-alliance-introduces-security-enhancements)

Encryption Types

Only the payload of data frames are encrypted in general cases. In some advanced cases, management frames can also be encrypted. Encryption here is targeted towards data frames.

None – No Encryption – Open Authentication, relying on application for encryption, not reliable. Suggested to use your personal VPN services to mitigate against any attacks. OWE – (Opportunistic Wireless Encryption) – may offer some encryption for open authentication in the near future. (https://tools.ietf.org/html/draft-wkumari-owe-00) 
TKIP (Temporal Key Integrity Protocol)- Introduced in 2002, Patch WEP (Wireless Encryption Protocol). It uses RC4 as its cipher, same as WEP.  You should refrain from using TKIP and upgrade your devices. Data rates are also limited to 54Mbps.
CCMP/AES (Counter Mode Cipher Block Chaining Message Authentication Code Protocol) – Strongest of all, not compromised till now. Suggested to use for your network. WPA/WPA2 – WPA uses TKIP, WPA2 uses CCMP/AES and TKIP as well.

Thanks to SemFio network for the diagram below.

In my own simple words  4-way handshake between a client and an access point

Acronyms used:

PMK - pairwise master key
PRF = Pseudo Random Function
AA = Authenticator Address, SA = Supplicant Address
PTK = PRF(PMK | ANonce | SNonce | AA | SA)
MIC = Message integrity code
GTK = Group temporal key 

1. EAP-Key Message 1/4 (ANonce) – AP to CLIENT
   As the first message is send from AP to client, this message includes a random number as ANonce for PTK generation at the client. Since the client knows its own SNonce and SA as well as the AA (from Beacons, Probe Response and/or Association Response) and PMK, the ANonce from this message is the only missing information.
2. EAP-Key Message 2/4 – CLIENT to AP (SNonce, MIC)
   As the Supplicant (client) replies to the first EAP Key message, the client sends the used SNonce as clear text to the AP “protected” by a cryptographic hash (HMAC-SHA1) called Message Integrity Code (MIC) for integrity of of this message the installed key on the client side. The AP will generate its own MIC and compare it the the one in this message, if they match, EAP-Key message 3 is send for key installation. This message also includes the Robust Security Network Information Element (RSN IE).
3. EAP-Key Message 3/4 – AP to CLIENT >

   Message 3 is the last unencrypted key message, as long as no retransmission(s) occur and the pairwise temporal key remains valid. The AP informs the client about the installation of the PTK and the receive sequence counter (RSC) for the GTK. The GTK itself is given in the WPA Key Data field, secured/encrypted with the PTK.

4. EAP-Key Message 4/4 CLIENT to AP
   

   The Supplicant acknowledges the installation of PTK and GTK afterwards, encrypted Unicast and Broad-/Multicast transmission can start now.

NOTE: The 4 Way Handshake happens after the open system auth or 802.11 association. WPA/2 right after the association. In case of 802.1x it happens after above process in the image.