H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 65)

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Figure 28 Shared key authentication process
WLAN data security
WLAN networks tend to be more susceptible to attacks than wired networks because WLAN devices
share the same transmission medium. As a result, the potential exists for one a device to intercept data
not intended for it. If no security is provided, plain-text data is at risk of being read by unintended
recipients.
To secure data transmission, 802.11 protocols provide some encryption methods to make sure devices
without the correct key cannot read encrypted data.
1. Plain-text data
All data packets are not encrypted. It is in fact a WLAN service without any security protection.
2. WEP encryption
Wired Equivalent Privacy (WEP) was developed to protect data exchanged among authorized
users in a wireless LAN from casual eavesdropping. WEP uses RC4 encryption for confidentiality.
WEP encryption falls into static and dynamic encryption according to how a WEP key is
generated.
• Static WEP encryption
With Static WEP encryption, all clients using the same SSID must use the same encryption key. If
the encryption key is deciphered or lost, attackers will get all encrypted data. In addition,
periodical manual key update brings great management workload.
• Dynamic WEP encryption
Dynamic WEP encryption is a great improvement over static WEP encryption. With dynamic WEP
encryption, WEP keys are negotiated between client and server through the 802.1X protocol so
that each client is assigned a different WEP key, which can be updated periodically to further
improve unicast frame transmission security.
Although WEP encryption increases the difficulty of network interception and session hijacking, it
still has weaknesses due to limitations of RC4 encryption algorithm and static key configuration.
3. TKIP encryption
Temporal key integrity Protocol (TKIP) and WEP both use the RC4 algorithm, but TKIP has many
advantages over WEP, and provides more secure protection for WLAN as follows:
{
First, TKIP provides longer IVs to enhance encryption security. Compared with WEP encryption,
TKIP encryption uses 128–bit RC4 encryption algorithm, and increases the length of IVs from 24
bits to 48 bits.