CovidPass: Making it badass by drawing inside the QR code

[hrvach]

As a small, useless but fun hobby project, I wanted to try and draw something inside my EU Covid Pass QR certificate WITHOUT relying on error correction or rendering the digital certificate invalid.

TL;DR - some deflate misuse, mixed-mode alphanumeric and numeric QR encoding, mask choice override, padding the code with content that base45 encodes to numbers only and choosing them in a way to produce a meaningful image. Apparently, verifier apps are fine with it - every one I tried scans green.

This is a non-prod demo cert used for illustration of the concept with some funny images inside:

https://i.imgur.com/3JonSRX.png

Would there be any interest in me doing a post explaining how it was done?

Also, what else should I draw inside?

[bellyfullofbac]

Neat. How about a pixel art that reads "Legit certificate of vaccination" in bad hand writing (like this[1]), but actually scans to a valid certificate?

TBH I didn't even notice the skull and syringe at first glance, just a QR code.

[1] https://papersplease.fandom.com/wiki/Jorji_Costava?file=Fake... vs legitimate passports in the game: https://steamtradingcards.fandom.com/wiki/Papers,_Please_-_P...

[hrvach]

Url link: https://i.imgur.com/3JonSRX.png

[muzani]

I love it. I probably wouldn't do it, but it's interesting, especially for those of us who have been doing QR code apps for years.

[JoshMandel]

What a delight! For sure would love to read the details.

[severine]

Definitely interested in a writeup!