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I'm looking to create a cheap air-gaped computing device to store and utilize sensitive data like cryptocurrency wallet addresses or PGP keys. Now, I'm a total newb when it comes to Raspberry Pi but they do seem suitable for these applications, save for the fact that most Pi boards have Wifi and Bluetooth built-in, which is actually undesirable in this case. The original Pi Zero doesn't have Wifi and Bluetooth built-in, but it's difficult to obtain from where I live, and it only has a single MicroUSB port for input, so a standard model might be preferable.

So my question is if and how I would be able to physically modify the board in order to disable wireless networking functionalities on a Pi Zero W or Pi 3? Alternatively, might it be feasible to simply shield the board or (ideally) the wireless components using a faraday bag or similar?

  • Your best bet if you don't like the Zero form factor is to look for a model 1B. I believe they are still in production, in any case they are still sold in a few places. – goldilocks Jul 2 at 17:18
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You could of course just break out the WLAN chip and bluetooth chip, respectively.
The WLan Chip should be the little thing with the raspberry icon on it.

But why'd you do this? Fear of getting hacked, ripped off?
You have multiple ways of protecting yourself if you feel paranoid....

LEARN USING LINUX: sudo ifconfig wlan0 down
this will disable your wlan chip per kernel command. Simple as that.
Oh, and if you don't use the general purpose raspbian kernel and instead use, let's say, arch linux, u can cut off wlan drivers from the beginning

USE CORRECT DEVICE: Bitcoin can be stored on tags. Yes, simple as that. RFID tags. And you can place these inside a lead box if you're still paranoid. Also you can obtain a physical bitcoin, a coin that has the value printed on it ( and consists of metal that has a value by itself, lol) Also, what is the point on not having the wallet on your smartphone, where you can use it to actually buy stuff with?

Are just 2 answeres that came to mind instantaniously.

But if you still wanna go for it, then do it like that: Carefully drill a hole in the chip, this would be the safest way of permanent disabling it without the risk of getting other stuff damaged that is around the wlan chip on the circuit board.

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    Awesome! Thanks for the thorough response. I'm not completely comfortable with a software approach, since at least in theory, any software modification can be reversed at some point if an attacker acquires indirect or physical access, and do this without my knowledge. In any case a Pi board is cheap and therefore expendable for something like this. – Morgan087 Jul 3 at 21:23
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I have done this on one of my Pi's following the instructions on this site

https://irulan.net/disable-wifi-and-bluetooth-on-raspberry-pi-3/

systemctl disable wpa_supplicant
systemctl disable bluetooth
systemctl disable hciuart

Add to /boot/config.txt:

Disable WiFi and Bluetooth

dtoverlay=pi3-disable-wifi
dtoverlay=pi3-disable-bt

Reboot.

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    This doesn't physically disable the wifi in a way effective enough to consider it air-gapped; malicious software on the device could simply re-enable it. – goldilocks Jul 2 at 17:15

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