<!-- Author: Xianjun jiao SPDX-FileCopyrightText: 2021 UGent SPDX-License-Identifier: AGPL-3.0-or-later --> [ACM WiSec 2021. Openwifi CSI fuzzer for authorized sensing and covert channels](https://dl.acm.org/doi/pdf/10.1145/3448300.3468255) CSI (Channel State Information) of WiFi systems is available in some WiFi chips and can be used for sensing the environment (keystrokes, people, object) passively and secretly. ## Concept How could a CSI fuzzer stop unauthorized sensing? ![](./csi-fuzzer-system-before-vs-now.png) CSI fuzzer implementation principle. ![](./csi-fuzzer-principle.png) ## Demo instructions Thanks to the full-duplex capability and CSI extraction feature of openwifi, you can monitor the artificial channel response via [side channel](./csi.md) by Tx-Rx over the air coupling without affecting the normal operation/traffic of openwifi. Before the self-monitoring, the auto-mute during Tx needs to be disabled. The full demo steps are: ``` ssh root@192.168.10.122 (password: openwifi) cd openwifi ./fosdem-11ag.sh (setup openwifi AP) ./sdrctl dev sdr0 set reg xpu 1 1 (Disable auto-muting to listen self-TX) insmod side_ch.ko num_eq_init=0 ./side_ch_ctl wh1h2001 ./side_ch_ctl wh6hffffffff (Let's only monitor self-beacon-TX CSI over-the-air loopback) ./side_ch_ctl g1 ``` Go to openwifi/user_space/side_ch_ctl_src, and run `python3 side_info_display.py 0`. You should see the over-the-air loopback CSI when CSI fuzzer is not enabled. Then stop the python3 side_info_display.py script to ease the next step. Start another ssh session to the openwifi board: ``` ssh root@192.168.10.122 (password: openwifi) cd openwifi ./csi_fuzzer_scan.sh 1 (CSI fuzzer applies possible artificial CSI by scanning all values) (csi_fuzzer.sh is called. Please read both scripts to understand these commands) ``` Go to openwifi/user_space/side_ch_ctl_src, and run `python3 side_info_display.py 0`. Now you should see that CSI keeps changing like in this [video](https://youtu.be/aOPYwT77Qdw). # Further explanation on parameters CSI fuzzer in openwifi system architecture and related commands. ![](./csi-fuzzer-implementation.png) # Example fuzzed CSI CSI self-monitoring before fuzzing. ![](./csi-fuzzer-beacon-ant-back-0.jpg) CSI self-monitoring after fuzzing command: `csi_fuzzer.sh 1 45 0 13` ![](./csi-fuzzer-beacon-ant-back-1-45-0-13.jpg) `csi_fuzzer_scan.sh` can scan the c1 and c2 in different styles/modes by calling `csi_fuzzer.sh`.