ZyXEL Access Point G1000 v2 91-005-124001B Manual Do Utilizador

ZyXEL G-1000 v2 User’s Guide

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In order to ensure network security, the access point and the RADIUS server use a shared 
secret key, which is a password, they both know. The key is not sent over the network. In 
addition to the shared key, password information exchanged is also encrypted to protect the 
network from unauthorized access. 

This appendix discusses some popular authentication types: EAP-MD5, EAP-TLS, EAP-
TTLS, PEAP and LEAP. 

The type of authentication you use depends on the RADIUS server or the AP. Consult your 
network administrator for more information.

MD5 authentication is the simplest one-way authentication method. The authentication server 
sends a challenge to the wireless station. The wireless station ‘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. 

With EAP-TLS, digital certifications are needed by both the server and the wireless stations 
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 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-TTLS supports EAP methods and legacy 
authentication methods such as PAP, CHAP, MS-CHAP and MS-CHAP v2.