Home > Articles > Cisco Network Technology > Security > EAP Authentication Protocols for WLANs

EAP Authentication Protocols for WLANs

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: Feb 18, 2005.

Chapter Description

This chapter examines the authentication methods: EAP, PEAP, LEAP, and the newer, emerging paradigm EAP-FAST, and weighs the pros and cons of each, in terms of standardization maturity and effectiveness.

From the Book

Cisco Wireless LAN Security

Cisco Wireless LAN Security

$66.99

EAP-FAST

Comparing the various methods, the EAP-FAST mechanism is the most comprehensive and secure WLAN scheme. LEAP was proven to be susceptible to dictionary attacks, and EAP-FAST is preferable to LEAP. In short, EAP-FAST is hardened LEAP with better crypto protecting the challenge/response mechanism.

EAP-FAST not only mitigates risks from passive dictionary attacks and man-in-the-middle (MitM) attacks, it also enables secure authentication based on currently deployed infrastructure. In addition, EAP-FAST minimizes the hardware requirement; many of the mechanisms require computational burden at the edge devices for asymmetric cryptography and certificate validation. As you have seen from your experience, secure-but-difficult-to-deploy mechanisms would not be popular; hence, EAP-FAST's features (such as flexible deployment model, support for secure provisioning, and efficiency) make it attractive for deployments.

To bootstrap the process securely, EAP-FAST establishes a shared secret (between the client and the authentication server) referred to as the Protected Access Credential Key (PAC-Key). The PAC consists of the PAC-Key (32 bytes), an opaque field cached by the server, and PAC info (metadata about the PAC). The PAC is used to establish a tunnel that is then used to perform authentication. The three-phase EAP-FAST protocol is shown in Table 7-3.

Table 7-3 EAP-FAST Phases

Phase

Function

Description

Purpose

Phase 0

In-band provisioning—provide the peer with a shared secret to be used in secure phase 1 conversation

Uses Authenticated Diffie-Hellman Protocol (ADHP)

This phase is independent of other phases; hence, any other scheme (in-band or out-of-band) can be used in the future.

Eliminate the requirement in the client to establish a master secret every time a client requires network access

Phase 1

Tunnel establishment

Authenticates using the PAC and establishes a tunnel key

Key establishment to provide confidentiality and integrity during the authentication process in phase 2

Phase 2

Authentication

Authenticates the peer

Multiple tunneled, secure authentication mechanisms


Figure 7-18 shows the functional entities involved in an EAP-FAST exchange. Of course, more than one function can be embedded in one server or software layer.

Figure 18Figure 7-18 EAP-FAST Functional Entities

EAP-FAST Frame Format

As shown in Figure 7-19, the EAP-FAST frame format is similar to the TLS format for phase 1.

Figure 19Figure 7-19 EAP-FAST Frame Format

The major contribution by EAP-FAST to the frame format is the PAC fields and associated information in the phase 0 and subsequent conversations. Figure 7-20shows the PAC-TLV.

Table 7-4 describes some of the salient fields.

EAP-FAST Choreography

The EAP-FAST choreography is a combination of multiple conversations. Figure 7-21 shows an overview of the EAP-FAST choreography.

Figure 20Figure 7-20 PAC TLV Frame Format

Table 7-4 Salient Fields in EAP-FAST

Name

Description

Relevance

A-ID

Authority identifier. This field would be in the EAP-FAST start frame.

A unique name identifying the authentication server. Will be used by the client/peer to index into the PAC and other context information.

I-ID

Initiator identifier.

A unique name identifying the peer/client.

CRED-LIFETIME

Expiration time of the credential.

This field will be in the PAC key info and used to validate a PAC key set.


Figure 21Figure 7-21 EAP-FAST Choreography Overview

Step 1

Step 1, of course, is to have connectivity between the client/peer and AP, in addition to secure connections between the AP, EAP-FAST server, and authentication server.

Step 2

To bootstrap a secure channel, the EAP phase 0 provisioning needs to be performed. This is done once per client setup. This phase itself is an EAP-TLS exchange, with the Diffie-Hellman key exchange and fields embedded in the TLS choreography. At the end of phase 0, the PAC between the peer/client and the authentication server is established.

Step 3

This is similar to the EAP identity exchange.

Step 4

This is the EAP-FAST start message, which includes the authenticator ID.

Steps 5, 6, and 7

TLS exchanges over EAP-FAST to authenticate the peer and the server. The client sends the PAC-opaque to the server in Step 5.

Step 8

Step 8, the inner authentication method, is where the actual authentication happens. The message exchange is implemented via EAP-TLV over EAP-FAST between the peer and the EAP server and most probably RADIUS between the EAP server and the authentication server. It is also possible that the same software in one computer performs both server functions. The phase 2 inner authentication method over EAP-TLV can be EAP-SIM, EAP-OTP, EAP-GTC, or MSCHAPv2.


Step 9

This is the mandatory EAP success message required by EAP.

Step 10

You can now use the key materials and contexts established by the three phases to use WPA methods to exchange information, thereby achieving confidentiality and integrity.


Cisco Press Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Cisco Press and its family of brands. I can unsubscribe at any time.

Overview

Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Cisco Press products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@ciscopress.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security

Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children

This site is not directed to children under the age of 13.

Marketing

Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out

Users can always make an informed choice as to whether they should proceed with certain services offered by Cisco Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.ciscopress.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links

This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020