1. 802.1x EAP Authentication Protocols
WIRELESS SECURITY
802.1x EAP Authentication Protocols

2. 802.1x - Authentication Methods
EAP defines a standard message exchange that allows a server to authenticate a client based on an authentication protocol agreed upon by both parties.
The access point relays authentication messages from the wireless client device to the RADIUS server and from the RADIUS server to the wireless client device.
Components involved in the 802.1x/EAP authentication process are:
supplicant (the end entity, or end user's machine),
the authenticator (the access point), and
the authentication server (back-end RADIUS server).
IEEE 802.1x is a port based authentication protocol

3. EAP – How It Works

4. 802.1x EAP – Authentication Types
A specific EAP authentication scheme is known as an EAP type.
Both the remote access client and the authenticator must support the same EAP type for successful authentication to occur.
The access point has to support the 802.1x/EAP authentication process. (The access point is not aware of the EAP authentication protocol type.)
The different EAP-Types are :
EAP-Transport Layer Security (EAP-TLS)
Tunneled Transport Layer Security (TTLS)
Cisco Light Weighted EAP (LEAP)
Protected EAP (PEAP).

5. EAP – TLS and its Disadvantages
In EAP-TLS, certificates are used to provide authentication in both directions.
The server presents a certificate to the client, and, after validating the server's certificate the client presents a client certificate.
Requires each user to have a certificate.
Imposes substantial administrative burden in operating a certificate authority to distribute, revoke and manage user certificates

6. EAP – TLS in Action

7. EAP- Tunneled Transport Layer Security (EAP- TTLS)
EAP - TTLS protocol developed in response to the PKI barrier in EAP-TLS.
TTLS a two-stage protocol - establish security in stage one, exchange authentication in stage two.
RADIUS servers, not the users, are required to have certificates
The user’s identity and password-based credentials are tunneled during authentication

8. Advantages of Using EAP – TTLS
Users to be authenticated with existing password credentials, and, using strong public/private key cryptography
Prevents dictionary attacks, man-in-the-middle attacks, and hijacked connections by wireless eavesdroppers.
Does not require the use of client certificates.
Requires little additional administration unlike EAP-TLS
Dynamic per-session keys are generated to encrypt the wireless connection and protect data privacy

9. Situations when EAP – TTLS can Fail
User's identity is not hidden from the EAP-TTLS server and may be included in the clear in AAA messages between the access point, the EAP-TTLS server, and the AAA/H server.
Server certificates within EAP-TTLS makes EAP-TTLS susceptible to attack.
EAP – TTLS is vulnerable to attacks by rogue EAP-TTLS servers

10. Comparison of EAP- TTLS and PEAP Protocols
Microsoft, Cisco and RSA Security developed Protected Extensible Authentication Protocol (PEAP) over WLANs
Windows XP is currently the only operating system that supports PEAP.
Only EAP - generic token card
Funk Software and Interlink Networks added support for the proposed wireless security protocol, developed by Funk and Certicom,
Linux, Mac OS X, Windows 95/98/ME, and Windows NT/2000/XP.
Any Authentication Method - CHAP, PAP, MS-CHAP, and MS-CHAPv2 and EAP

11. Conclusions
Selection of an authentication method is the key decision in securing a wireless LAN deployment.
EAP-TLS is best suited under situations when a well configured PKI is already deployed
TTLS slight degree of flexibility at the protocol level and supports wider of client operating systems.
No single security solution is likely to address all security risks. Hence should implement multiple approaches to completely secure wireless application access

12. References