Stronger WEP keys are provided by TKIP enhancements such as MIC. MIC
prevents bit-flip attacks on encrypted packets. It is shown in Figure
. During a
bit-flip attack, an intruder intercepts an encrypted message, alters it
slightly, and retransmits it. The receiver accepts the retransmitted message as
legitimate. The client adapter driver and firmware must support MIC
functionality, and MIC must be enabled on the access point. TKIP enhancements,
such as MIC and WEP Key hashing, can be enabled by using static WEP keys. They
do not need a RADIUS server to function.