The Tinfoil Chat setup uses optocouplers to enforce one-way data transmission.[0] And one can use inexpensive CD-R and micro SD cards for single-use data transfer. But transferring anything but plain text is dangerous.
Thanks for mentioning the octocouplers implementation, it looks very interesting and I'll look it. Other options I'm aware of to avoid USB and complex drivers/protocols:
I wonder if one could cut up QR codes, and store pieces separately. If that were done in Gimp or whatever, there could be multiple copies of each piece.
I meant actually cutting them with a sharp knife, or scissors. So you could hide pieces in different places. For stuff like URLs, passphrases, wallet seeds, etc.
The Tinfoil Chat setup uses optocouplers to enforce one-way data transmission.[0] And one can use inexpensive CD-R and micro SD cards for single-use data transfer. But transferring anything but plain text is dangerous.
0) https://github.com/maqp/tfc