[Cryptography] cryptography Digest, Vol 50, Issue 18

[Grant Schultz]

Bear wrote,
> The uncrackable is difficult.
> A single cell phone is difficult.   However two devices could be less hackable.
> An old cell phone can be side loaded with an application in developer mode
> and kept in airplane mode and air gaped.
As long as the old phone is permanently air-gapped.  If you ever upload 
new software to it, malware could jump the gap.  This would be an even 
greater risk if you're using freely-available software that was already 
known to the 3-letter agencies, as their trojans would be scanning for 
known packages.

Even with photographing of QR codes, information could be exfiltrated 
from a phone, perhaps by displaying a blinking pixel someplace, which 
the other phone's camera would pick up.

Grant