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Normally, I avoid using any Bluetooth or wireless devices, especially HIDs, but for a project I am working on the only keyboards that will fit the size are Bluetooth and wireless keyboards, so I am stuck having to use one.

To that end, I am looking for ways to make using one more secure, if not exactly secure. Here are things I am considering:

  1. With devices connected by WiFi, attackers first have to deauthenticate the target before hijacking its connection. The deauthentication packet/s sent can usually be detected by running a packet sniffer. Does hijacking a Bluetooth have a similar step of having to issue a deauthentication packet, and if there is, is there a way to detect it?

  2. If the Bluetooth/wireless keyboard sits directly on top of/beside the device used with extremely little to no distance between them, does this affect an attacker's ability to fool the target computer into letting it connect his device to the device? Are there any ways to mitigate risks from this if not remove them? Is there a way to use the fact of the unchanging distance between the keyboard and the device to help protect against attempted hijacking of the connection?

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It's always incredibly tough to know what standard (if any) a cheap wireless peripheral is using. BLE (if used, properly) specifies pairing with encryption for HID profiles. So hijacking shouldn't be possible.

A link with an encryption key unknown to the attacker that cannot be convinced to change it's key to one the attacker has access to shouldn't allow the attacker to connect no matter the distance. Without control over either wireless stack there's likely not much that can be done to leverage known distance. The most interesting (unrealistic?) approach being breaking open the devices, adding a 50 ohm impedance SMA/SMC connector to both devices and hard wiring them. Extra points for severing as much of the antenna trace/chip as possible.

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  • Hi, thanks for answering. Since the Bluetooth keyboard I have is a cheap one and practically came with no instructions or descriptions, I'm not sure about encryption. But it's the one that best fits my project given the case I'm using for it (a 3D printed) case. Will lining it with something like foil or some other conductive material, effectively making a Farady Cage, help make it secure? I'm looking to try to bring the risks down to zero or as close to zero as possible.
    – user942937
    Commented May 27, 2022 at 4:08
  • Now we're getting into my physics knowledge which is much shakier. I think a Faraday cage requires earth grounding. Ungrounded metal with holes no larger than 1/2 wavelength of a given signal will reflect RF. So consider where the antenna is and where you plan to place the metal and draw imaginary rays extending from the antenna in all directions, bouncing off the metal like a mirror to figure out vaguely where the signal might go. And remember RF will try to escape through any nonmetal hole available, the smaller the hole relative to it's wavelength, the weaker it will be once it gets out
    – foreverska
    Commented May 27, 2022 at 14:30

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