A script to split long(e.g. 4096 bits) private keys into qr codes so you could print on a paper.

paperkey.sh

#!/bin/sh

# Q&As
#
# Q: Why not use [paperkey][paperkey]? 
# A: It brings much more complexity and dependencies, and I don't have time to check the implementation for security.
#
# Q: Why not OCR?
# A: I didn't find an open-source ocr software that works for normal photos.
#    even though I used [OCR-A][OCR-A] for printing and [ScannerPro][ScannerPro] for image processing.
#
# [paperkey]: http://www.jabberwocky.com/software/paperkey
# [OCR-A]: https://en.wikipedia.org/wiki/OCR-A
# [ScannerPro]: https://readdle.com/scannerpro

# Dependencies
# - split
# - qrencode https://fukuchi.org/works/qrencode/index.html.en

dump() {
	out_dir=$1

	if ! mkdir -p "$out_dir"; then
		exit 1
	fi

	split -a 1 -b 2600 - "$out_dir/key_part."

	for part in "$out_dir/"key_part.*; do
		#dmtxwrite -o "$part.png" < "$part"
		qrencode -o "$part.png" -r "$part"
	done
}


main() {
	dir=${2-output}

	dump "$dir"
	echo "Usage: $0 [output-dir] < key-file"
}

main "$@"