Zhone zNID-GPON-2402 Configuration Manual page 115

Configuration pages
Shared
Shared network authentication uses WEP encryption that must be shared
between the AP and the STA. The initial request from the STA is in clear text,
as is the challenge from the AP. The STA replies to the challenge with the
Network Key in an encrypted message.
Figure 83: Wireless security with Shared network authentication
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zNID 24xx Series Configuration Guide