User's Manual

Reference Manual for the Model CG814W Wireless Cable Modem Gateway
Networks, Routing, and Firewall Basics B-15
Shared Key Authentication
The following steps occur when two devices use Shared Key Authentication:
1. The station sends an authentication request to the access point.
2. The access point sends challenge text to the station.
3. The station uses its configured 64-bit or 128-bit default key to encrypt the challenge text, and
sends the encrypted text to the access point.
4. The access point decrypts the encrypted text using its configured WEP Key that corresponds
to the station’s default key. The access point compares the decrypted text with the original
challenge text. If the decrypted text matches the original challenge text, then the access point
and the station share the same WEP Key and the access point authenticates the station.
5. The station connects to the network.
If the decrypted text does not match the original challenge text (i.e., the access point and station do
not share the same WEP Key), then the access point will refuse to authenticate the station and the
station will be unable to communicate with either the 802.11b network or Ethernet network.
This process is illustrated in below.
Figure 6-5: 802.11b shared key authentication
INTERNET LOCAL
ACT
12345678
LNK
LNK/ACT
100
Cable/DSL
ProSafeWirelessVPN SecurityFirewall
MODEL
FVM318
PWR TEST
WLAN
Enable
Access Point1) Authentication
request sent to AP
2) AP sends challenge text
3) Client encrypts
challenge text and
sends it back to AP
4) AP decrypts, and if correct,
authenticates client
5) Client connects to network
802.11b Authentication
Shared Key Steps
Cable or
DLS modem
Client
attempting
to connect