On Mon, Oct 12, 2020, 6:57 PM grarpamp <[1]grarpamp@gmail.com> wrote:

     > usbs have microchips that accept code updates
     USB "converters" should be considered suspect.
     Plugging BadUSB's, BadHDD, CPU's, Flash, or any
     other chipped / smart device or port with firmware, microcode,
     chips etc between systems has potential to infect / attack them.

   How would you set up an airgapped system, if your main system were
   already infected?  There's some degree of number of microchips, times
   accessed, way and source of system installation and tools added ...
   On a pi zero, you're likely going to have a keyboard, a display, and an
   SD card, all of which have additional chips, some even long wires that
   can act as radios.  Then the communication medium; I guess using the
   existing display and keyboard adds the least complexity, but that's a
   lot of copying of encrypted text.  I might start with a USB key even
   though it busts a hole in the system, and just recommend it be moved
   very rarely.
   A second paired system could be used for data exchange, connected to a
   printer or a camera or a disk or whatnot, with an optoisolated gpio
   connection to the main system.

     Assuming some random magical usb converter
     cable sets do pass raw rs-232 between them
     (ie: can cut/splice to a rs-232 port / modem / teletype)

   The FTDI actually does this.

     users often probably fuck up and cross infect
     usb during the n-th insertion setup session.

   That sounds concerning.

     Various "air gap", all adaptable to 'cat hugefile > /device'...

   Prefer tinyclearfile to hugefile, so auditing is reasonable.

     QR code

     OCR scanning

     Sound

     Light
     RF
     Keyboard bots
     Monitor display output to camera capture input,
     a digital stream of bits thrown onscreen as fast
     as the two can sync.
     Simple RS-232 protocols, ECC codes, etc.
     All assuming endpoint chipsets don't attack over the gap / wire.
     Keep simple enough to see, log, debug, verify, filter, audit... like
     ASCII.
     USB, optical disk, tape, hdd... often have media
     based firmware update mechanisms, exploits,
     special sectors, bootcode, emulation, etc.

     > scrabble tiles
     As received from the store... exhibit a non-random
     character frequency count, should not be used without
     adjustment down to 1:1.

References

   1. mailto:grarpamp@gmail.com