ST

This is a part of TKIP Primer video series. The last few videos explain about the problems in WEP and how WPA-TKIP tries to mitigate most of them, without replacing the hardware. This video explains more about how the TKIP packets are decrypted with the help of key stream and the TSC (TKIP Sequence Counter). TKIP decapsulation process is essentially similar to encapsulation. After recovery of the TSC from the received packet, the TSC is examined to ensure that the packet just received has a TSC value greater than the previously received packet. If it does not, the packet is discarded in order to prevent potential replay attacks. Also, after the MIC value has been calculated based on the received and decrypted MSDU, the calculated MIC value is compared to the received MIC value. If the MIC values do not match, the MSDU is discarded and countermeasures are then invoked. These countermeasures consist primarily of rekeying the temporal key while controlling the rate at which this happens and sending alerts to network administration for follow-up.