ZyXEL Communications VSG1432-B101 - V1.10, Manual

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Appendix D Wireless LANs
VSG1432-B101 Series User’s Guide
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EAP (Extensible Authentication Protocol) is an authentication protocol that runs on
top of the IEEE 802.1x transport mechanism in order to support multiple types of
user authentication. By using EAP to interact with an EAP-compatible RADIUS
server, an access point helps a wireless station and a RADIUS server perform
authentication.
The type of authentication you use depends on the RADIUS server and an
intermediary AP(s) that supports IEEE 802.1x.
For EAP-TLS authentication type, you must first have a wired connection to the
network and obtain the certificate(s) from a certificate authority (CA). A certificate
(also called digital IDs) can be used to authenticate users and a CA issues
certificates and guarantees the identity of each certificate owner.
EAP-MD5 (Message-Digest Algorithm 5)
MD5 authentication is the simplest one-way authentication method. The
authentication server sends a challenge to the wireless client. The wireless client
‘proves’ that it knows the password by encrypting the password with the challenge
and sends back the information. Password is not sent in plain text.
However, MD5 authentication has some weaknesses. Since the authentication
server needs to get the plaintext passwords, the passwords must be stored. Thus
someone other than the authentication server may access the password file. In
addition, it is possible to impersonate an authentication server as MD5
authentication method does not perform mutual authentication. Finally, MD5
authentication method does not support data encryption with dynamic session
key. You must configure WEP encryption keys for data encryption.
EAP-TLS (Transport Layer Security)
With EAP-TLS, digital certifications are needed by both the server and the wireless
clients for mutual authentication. The server presents a certificate to the client.
After validating the identity of the server, the client sends a different certificate to
the server. The exchange of certificates is done in the open before a secured
tunnel is created. This makes user identity vulnerable to passive attacks. A digital
certificate is an electronic ID card that authenticates the sender’s identity.
However, to implement EAP-TLS, you need a Certificate Authority (CA) to handle
certificates, which imposes a management overhead.
EAP-TTLS (Tunneled Transport Layer Service)
EAP-TTLS is an extension of the EAP-TLS authentication that uses certificates for
only the server-side authentications to establish a secure connection. Client
authentication is then done by sending username and password through the
secure connection, thus client identity is protected. For client authentication, EAP-