For those who want more information on CSI (Channel State Information): http://dhalperi.github.io/linux-80211n-csitool/ http://dhalperi.github.io/linux-80211n-

For those who want more information on CSI (Channel State Information): http://dhalperi.github.io/linux-80211n-csitool/ http://dhalperi.github.io/linux-80211n-csitool/ This allows you to use a custom firmware developed for the Intel 5300 wireless adapter and read the CSI values with each packet. Every 802.11n implementation that I am aware of keeps a CSI vector (IQ values, typically as integers) within the wifi chip. Both the Wifi AP and STA do this. The CSI vector is updated with every packet, using the training data at the beginning of the packet. (802.11 is CSMA [2] so there is a fixed transmission to start the packet) In other words, Intel has this nice tool for one of their (now somewhat dated) chips. But CSI is not restricted to Intel chips. Atheros chips have a decent but limited CSI readback method, not quite as nice as Intel's [3]. But CSI has been used for experiments on all major wifi chips out there. With 802.11n this is used to determine the quality of signal likely to be received on each sub-carrier within the signal. CSI is useful for many other things: RF experiments, indoor position sensing, and now apparently also password cracking. [2] https://en.wikipedia.org/wiki/Carrier_sense_multiple_access_with_collision_avoidance https://en.wikipedia.org/wiki/Carrier_sense_multiple_access_... [3] http://pdcc.ntu.edu.sg/wands/Atheros/ http://pdcc.ntu.edu.sg/wands/Atheros/