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The Alphabet Soup of EAP types - MD5, LEAP, PEAP, FAST, TLS and TTLS
Note: This data is not intended for home or small-office users who typically do not use advanced security features such as those discussed within this page. However, these users may find the topics interesting for informational purposes.
802.1x Very Brief Overview
It is a port access protocol for protecting networks via authentication. As a result, this type of authentication method is extremely useful in the wireless environment due to the nature of the medium. If a wireless user is authenticated via 802.1x for network access, a virtual port is opened on the access point allowing for communication. If not successfully authorized, a virtual port is not made available and communications are blocked.
There are three basic pieces to 802.1x authentication:
- Supplicant - a software client running on the wireless workstation
- Authenticator - the wireless access point
- Authentication Server - a authentication database, usually a radius server such as Cisco ACS*, Funk Steel-Belted RADIUS*, or Microsoft* IAS*
EAP (extensible authentication protocol) is used to pass the authentication information between the supplicant (the wireless workstation) and the authentication server (Microsoft IAS or other). The actual authentication is defined and handled by the EAP type. The access point acting as authenticator is only a proxy to allow the supplicant and the authentication server to communicate.
Which to use?
Which EAP type to implement, or whether to implement 802.1x at all, depends upon the level of security that the organization needs and the administrative overhead/features desired. Hopefully the descriptions here and a comparative chart will ease the difficulties in understanding the variety of EAP types available.
Extensible Authentication Protocol (EAP) Authentication Types
Because WLAN security is essential and EAP authentication types provide a potentially better means of securing the WLAN connection, vendors are rapidly developing and adding EAP authentication types to their WLAN access points. Some of the most commonly deployed EAP authentication types include EAP-MD-5, EAP-TLS, EAP-PEAP, EAP-TTLS, EAP-Fast, and Cisco LEAP.
- EAP-MD-5 (Message Digest) Challenge is an EAP authentication type that provides base-level EAP support. EAP-MD-5 is typically not recommended for wireless LAN implementations because it may allow the user's password to be derived. It provides for only one way authentication - there is no mutual authentication of wireless client and the network. And very importantly it does not provide a means to derive dynamic, per session wired equivalent privacy (WEP) keys.
- EAP-TLS (Transport Layer Security) provides for certificate-based and mutual authentication of the client and the network. It relies on client-side and server-side certificates to perform authentication and can be used to dynamically generate user-based and session-based WEP keys to secure subsequent communications between the WLAN client and the access point. One drawback of EAP-TLS is that certificates must be managed on both the client and server side. For a large WLAN installation, this could be a very cumbersome task.
- EAP-TTLS (Tunneled Transport Layer Security) was developed by Funk Software and Certicom, as an extension of EAP-TLS. This security method provides for certificate-based, mutual authentication of the client and network through an encrypted channel (or "tunnel"), as well as a means to derive dynamic, per-user, per-session WEP keys. Unlike EAP-TLS, EAP-TTLS requires only server-side certificates.
- EAP-FAST (Flexible Authentication via Secure Tunneling) was developed by Cisco. Instead of using a certificate, mutual authentication is achieved by means of a PAC (Protected Access Credential) which can be managed dynamically by the authentication server. The PAC can be provisioned (distributed one time) to the client either manually or automatically. Manual provisioning is delivery to the client via disk or a secured network distribution method. Automatic provisioning is an in-band, over the air, distribution.
- LEAP (Lightweight Extensible Authentication Protocol), is an EAP authentication type used primarily in Cisco Aironet WLANs. It encrypts data transmissions using dynamically generated WEP keys, and supports mutual authentication. Heretofore proprietary, Cisco has licensed LEAP to a variety of other manufacturers through their Cisco Compatible Extensions program.
- PEAP (Protected Extensible Authentication Protocol) provides a method to transport securely authentication data, including legacy password-based protocols, via 802.11 wireless networks. PEAP accomplishes this by using tunneling between PEAP clients and an authentication server. Like the competing standard Tunneled Transport Layer Security (TTLS), PEAP authenticates wireless LAN clients using only server-side certificates, thus simplifying the implementation and administration of a secure wireless LAN. Microsoft, Cisco and RSA Security developed PEAP.
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802.1x EAP Types
Feature / Benefit |
MD5
---
Message Digest 5 |
TLS
---
Transport Level Security |
TTLS
---
Tunneled Transport Level Security |
PEAP
---
Protected Transport Level Security |
FAST
---
Flexible Authentication via Secure Tunneling |
LEAP
---
Lightweight Extensible Authentication Protocol |
| Client side certificate required |
no |
yes |
no |
no |
no
(PAC) |
no |
| Server side certificate required |
no |
yes |
no |
yes |
no
(PAC) |
no |
| WEP key management |
no |
yes |
yes |
yes |
yes |
yes |
| Rogue AP detection |
no |
no |
no |
no |
yes |
yes |
| Provider |
MS |
MS |
Funk |
MS |
Cisco |
Cisco |
| Authentication Attributes |
One way |
Mutual |
Mutual |
Mutual |
Mutual |
Mutual |
| Deployment Difficulty |
Easy |
Difficult (because of client certificate deployment) |
Moderate |
Moderate |
Moderate |
Moderate |
| Wireless Security |
Poor |
Very High |
High |
High |
High |
High when strong passwords are used. | |
A review of the above discussions and table will usually provide the following conclusions:
- MD5 is not typically used as it only does a one-way authentication, and perhaps even more importantly does not support automatic distribution and rotation of WEP keys so does nothing to relieve the administrative burden of manual WEP key maintenance.
- TLS, while very secure, requires client certificates to be installed on each wireless workstation. Maintenance of a PKI infrastructure requires additional administrative expertise and time in addition to that of maintaining the WLAN itself.
- TTLS addresses the certificate issue by tunneling TLS, and thus eliminating the need for a certificate on the client side. Making this an often preferred option. TTLS is primarily promoted by Funk and there is a charge for supplicant and authentication server software.
- LEAP has the longest history, and while previously Cisco proprietary (works with Cisco wireless adapters only), Cisco has licensed LEAP to a variety of other manufacturers through their Cisco Compatible Extensions program. A strong password policy should be enforced when LEAP is used for authentication.
- EAP-FAST is now available for enterprises that cannot enforce a strong password policy and do not want to deploy certificates for authentication.
- The more recent PEAP works similar to EAP-TTLS in that it does not require a certificate on the client side. PEAP is backed by Cisco and Microsoft and is available at no additional cost from Microsoft. If desired to transition from LEAP to PEAP, Cisco's ACS authentication server will run both.
Data Privacy
Data privacy is accomplished by use of a confidential key to encrypt data before transmission and then decrypt (recover the plain data) at the receiving end. Wired Equivalent Privacy (WEP) affords relatively weak security; therefore, other methods such as WPA and WPA2 have been developed to better protect wireless data.
WPA* (Wi-Fi* Protected Access)
The Wi-Fi Alliance introduced this standards-based solution in late 2003 in their effort to develop a more robust wireless LAN security solution to meet the 802.11i amendment. WPA includes 802.1x authentication and TKIP encryption (a more advanced and secure form of WEP encryption).
WPA2* (Wi-Fi Protected Access 2)
The Wi-Fi Alliance announced this second-generation of WPA security in late 2004. Like WPA, WPA2 also includes 802.1x authentication. Based on the 802.11i amendment, WPA2 protects data privacy with the Advanced Encryption Standard (AES.)
WPA Personal & WPA2 Personal
For small offices and home users where an authentication server is not available, authorization for access is determined by the use of a Pre-Shared Key (PSK.) The pre-shared key is a hexadecimal string or a pass phrase that must match between the access point and all clients. No 802.1x security is available when using WPA Personal or WPA2 Personal methods.
Other Security Options
VPN
Instead of relying on wireless LAN for authentication and privacy (encryption), many enterprises implement a VPN. This is done by placing the access points outside the corporate firewall and having the user tunnel in via a VPN Gateway - just as if they were a remote user. The downsides of implementing a VPN solution are cost, initial installation complexities, and ongoing administration overhead.
This applies to:
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