
Paper storage and recovery of GPG keys - ingve
http://www.saminiir.com/paper-storage-and-recovery-of-gpg-keys/
======
pwg
From the article: "Scan the QR codes from the paper as JPEG, for example."

Don't scan as JPEG. Barcodes (QR codes are a subset of general "barcodes") are
images that have very high contrast edges (typically a transition from pure
white to pure black or pure black to pure white) and the fidelity of that edge
is important to correctly decoding the code.

High contrast edges are the worst case for the JPEG compression algorithm, and
the algorithm produces the most noise (compression artifacts) for high
contrast edges (due to the nature of how the JPEG compression algorithm
operates).

So combining JPEG compression with barcode images you have the worst two
possible combinations, an algorithm that prefers nice sharp transitions
(barcodes) and an algorithm that will create blurry edges (JPEG on high
contrast edges).

Scan to PNG or old GIF or TIFF (using non-JPEG compression) but don't use JPEG
for this particular purpose.

