Increase entropy

[Deleplace]

Find out by how many characters we can increase the size of the secret in the QR-code, without triggering any increase of the QR resolution (total number of black/white squares)

[Deleplace]

Before

• QR code Error Correction level M (15% error correction capability)
• 14 letters with an alphabet of 62 characters ~= 83 bits of entropy
• resulting QR code resolution: 25x25 (good, easy to scan)

After

• QR code Error Correction level L (7% error correction capability)
• 21 letters with an alphabet of 64 characters == 126 bits of entropy
• The 2 new accepted letters in the alphabet are -, (dash) . (dot)
• resulting QR code resolution: 25x25 (good, easy to scan)

The expectation is that QR codes on screen are not damaged, thus error correction level L should usually be enough.

[Deleplace]

Logs show this change did not negatively impact the scan duration. The time it takes to scan the QR code is 6300ms on average.