Wanted: Faraday cage that allows for QR code data transfer

[CIYAM]

After having read about the various "side-channel" attacks that will happen with anything that is "connected" I have come to the conclusion that the best way that you can "secure" cryptographic keys is by using a smart phone that is permanently surrounded by a Faraday cage.

I have discussed the problem of charging such a phone and from what I understand shielding all but extremely low frequencies will prevent side-channel attacks but would still allow for DC charging and also if the material is transparent enough for QR codes then charging using solar should be possible (although am not sure how practical that would be with current technology).

Why use a (smart) mobile phone?

Simply because it is the cheapest device that will do QR codes, has a camera and has enough processing power to do the cryptographic things like signing offline txs.

Such a device could also be used for doing QR code "logins" such as has been developed here: https://bitcointalk.org/index.php?topic=310282.0

There was a crowd-funded project that created a "Faraday cage pouch" for mobile funds a few years back (sorry can't find the link now) so perhaps this idea could be done in a similar way (I am not wanting to have any "ownership" of anything for this idea).

My understanding is that the same tech that is used to create "tinted windows" can actually be applied to creating "see through Faraday cages" which would then allow QR codes to be used for data transfer (the safest way I think transfers can be done).

As far as doing Bitcoin txs "offline" via QR codes I developed the CIYAM Safe (https://susestudio.com/a/kp8B3G/ciyam-safe) some years back - I'm not sure if that would be suitable for mobile phones but I would be happy to help a savvy developer to work out how to do the same thing on Android and/or iOS.

[hexafraction]

I'm not sure if an imperfect faraday cage will protect against radio side channel attacks such as those seen on Elgamal. It would need to be done quite well to cover most frequencies with a fairly high percentage of attenuation or inject noise of its own.

[CIYAM]

I'm not sure if an imperfect faraday cage will protect against radio side channel attacks such as those seen on Elgamal. It would need to be done quite well to cover most frequencies with a fairly high percentage of attenuation or inject noise of its own.

My understanding (from talking to an electronics expert) is that all frequencies above say 10 Hz could be protected (assuming charging will be done this way) and that a "side-channel" attack with 10 Hz would not be likely to be a serious vulnerability (but I am no expert).

[achow101]

If the faraday cage's gaps are big enough to let light through, then I would think that a small USB cable could fit through the gaps to charge the phone.

[hexafraction]

I'd assume a fine mesh would be necessary over the screen for any protection.