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Using QR codes sets you up for disappointment. I wanted to store a gpg key offline by engraving it in metal. A reasonably sized one would taken six of the larg
by kongin 5y ago
Using QR codes sets you up for disappointment.
I wanted to store a gpg key offline by engraving it in metal. A reasonably sized one would taken six of the largest 177x177 plates to record.
The best solution I came up with was to use metallic punched tape of some description.
- mekkkkkk 5y agoA v40 QR code can hold ~3000 chars/bytes. Isn't that enough for a GPG key?
- kongin 5y agoIt's been over two years since I looked at it, but from memory I wanted a 8 KiB key pair that I could engrave. One was to be the public key that would be scannable, the other was the private key that would be kept in a safety deposit box. The practical limit was 3KiB for the qr code and there was some metadata in the key I didn't want to lose. I can't remember if it was the private or public key that was giving me the most trouble. But the idea of just having something to point your phone at on a wall and read a signed message from me wasn't practical.
- dtonon 5y agoOn low error correction level you can save 2953 bytes in binary and 4296 in alphanumeric mode. The latter should be fine for a gpg key. I'm experimenting for fun on this side: https://github.com/dtonon/papiro https://github.com/dtonon/papiro
- dtonon 5y agoMy fault: alphanumeric mode is not suitable for a GPG key, because it is: > 0–9, A–Z (upper-case only), space, $, %, *, +, -, ., /, : and so we miss the lowercase [a-z]. Therefore we need to use the 2953 bytes binary option.